To ensure that a knife is sharp for faster, easier,and safer work, one should follow these basic principles:

1. Select an appropriate knife for the task.
2. Select a knife of quality construction and materials.
3. Use appropriate sharpening tools.
4. Use an appropriate sharpening technique.

Most knives are made from:

Carbon steel
Merits
(a) Usually lower priced than high qualitystainless steel knives.
(b) Easily sharpened
(c) Remains sharp longer than stainless steelknives
 Limitations
(a) Rusts easily
(b) Vulnerable to tarnish and discolorationB.

Stainless steel
Merits
(a) Resistant to rust, tarnish and discoloration

Limitations
(a) Usually more expensive than similarcarbon steel knives
(b) low priced stainless steel knives are difficult to sharpen and do not easily maintain a sharp edge
(c) Poorly constructed stainless steel knives may be too thin and too flexible

Other materials and parts of the knife used are:
Titanium-Ceramic-Forged-Stamped

Prats of the knife are:
Tang-Bolster-Handle-Flat

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SELECTION 

CHEF'S KNIFE (French Chef's Knife), probably the most used knife in the kitchen.
Has a very broad blade and can range in length from six to twelve inches, eight inches is the most popular.
Used for all the chopping, mincing and dicing tasks and is essential for vegetables.
This knife is generally used on a cutting board by rocking it on it's curving edge, using the tip as a  pivot. Its broad blade keeps knuckles from hitting the cutting board.
Use its back to break chicken bones and scrape foods from the board. Use the flat side for crushing things like garlic.

Chinese Chef's Knife
(Chinese Cleaver because its similar shape to a meat cleaver)
The Japanese prefer a version with not as broad a blade, called Usuba, which most westerners find easier to handle, since its size more closely approximates the Chef's Knife.
Use only its back to break chicken bones, and also to scrape foods from the board. Use the flat side for crushing things like garlic.

Paring Knife
Has a short blade, usually no more than four inches in length, and in a variety of shapes and curves.
Used to peel, carve and prepare vegetables, fruit and other foodstuffs that can be held in the hand. Handiest for close-up work like eyeing potatoes, and great for boning chicken. But it is unsuitable for large, unwieldy pieces.

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Slicing Knife 
Has a very narrow, thin blade, eight to twelve inches long, used to cut very thin slices of  meats. The more flexible it is, the easier it will be to get a thin slice.
Some slicers have a curving or scimitar-style tip to assist in tight spots, like between wing and breast of chicken.
Smaller slicing knives, like sushi knives, are only sharpened on one side, so as to lessen resistance on the flat side and thus get a thinner slice.
Ceramic knives in general make excellent slicers because of their thinness and incredible sharpness.

Utility Knife
This all-purpose knife is usually about six inches in length and narrow. People who feel that a chef's knife is too large will find this knife easier to use. Use it also when you feel that a paring knife is too small for a task.

Bread Knife
This type of knife has serrated edges, enabling it to pierce a hard crust or skin (like tomatoes) without bruising or crushing the delicate insides. Measures five to twelve inches. These cannot usually be easily resharpened, but because the primary cutting edge is in the curved part of each serration, they rarely need sharpening.

Ham Slicer
(Granton) is different  from a regular Slicing Knife by its edge. What may look like a series of serrations are actually hollows along the edge of a flat blade, alternating in location between the two sides. The air pockets in these hollows keep food from sticking to the blade, consequently producing ultra-thin slices from most fish and boneless meats.
Great for slicing Roast Beef, Ham or Lox.

Fillet Knife
Like the Boning Knife, its thin blade is six-and-a-half to nine inches in length and should be quite flexible, great for filleting fish or chicken.

Clam and Oyster Knives -
Both have very short, broad blades, usually one to three inches in length. The clam knife is longer with a rounded tip and the oyster knife, with a protective hand shield, is shorter and has a sharp tip.

Cook's Knife
Sized between a chef's knife and a utility knife.
can be more comfortable to use because of its size.

Cleaver
The very broad, thick blade and heavy weight of this knife make easy work of cutting bone, splitting ribs and getting through cartilage
Does not chip easily.

Boning Knife
Usually five to six-and-a-half inches in length, has a very narrow blade, straight or curved.
A stiff boning knife is good for boning beef, a flexible boning knife is preferred for poultry.

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Miscellaneous knives include:

Mezzaluna -
This half moon-shape knife has a rounded blade (or blades) with handles at each end that are perpendicular to the cutting surface. A smaller version of this knife has one handle at the center of the blade. A Mezzaluna is used to mince foods on a cutting board or in a wooden bowl and is perfect for herbs and nuts.

Grapefruit knife serrated on both sides with a curved tip,
Frozen food knife with saw-like teeth

Cheese
With cut-out in the flat of the blade or a non-stick edge, and an upturned pointed tip for serving; short, wide and pointed for hard cheeses or 12" or longer and with two handles for slicing large rounds of cheese)
Sushi
With only one edge sharpened to get a thinner slice

High-Carbon Steel  no longer widely available. Professionals agree this is the best metal used for cutlery primarily because it holds an excellent edge and is quite easy to sharpen. It is somewhat brittle, so care should be taken not to drop it. It has a tendency to rust if it is not dried thoroughly after use, just scour and keep using it if it rusts. And because of steel's reaction to acids and alkalis, it can easily discolor; but this does not affect the other good qualities of this type of knife.


High-Carbon Stainless Steel -
This alloy has become the most popular of metals used in knife construction because of its rust and stain resistant quality. It does not hold its edge quite as well as high-carbon steel and is not quite as easy to sharpen; nevertheless, its convenience and ready availability make it the most popular choice in better cutlery.

Stainless Steel
This alloy is so hard that it strongly resists sharpening. Although it remains sharp longer, once it loses its edge it can become another disposable item. Recent advances in technology have produced some never-need-sharpening knives that do hold up for many years. Note that knives in this class almost always lack the quality, balance and feel of good tools. They remain a viable alternative for those who do not wish to care for or to sharpen their cutlery.

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Titanium
The better titanium knives are made with a sintering process on a matrix of titanium (Ti) and carbides (carbon combination), using powder metal technology (instead of metal casting). The sintering process melts the elements and recombines them under great heat and pressure. The carbides in the alloy allow for the blades to be heat-treated to a hardness appropriate for cutlery. Very lightweight and durable, they stay sharper longer than steel and are relatively easy to sharpen.
Titanium coated, or titanium edged, knives do not have the same quality as those made wholly of titanium or titanium and alloys, and have a relatively short useful lifespan, since the edge hardness is usually lost after a few sharpenings.

Ceramic 
This material is both strong and brittle. It is stronger than steel and has an edge that is remarkably thinner than steel, so cutting is made considerably easier, and the edge can last significantly longer with proper care. Because of their brittleness, relative to steel, ceramic knives are best used for slicing (not chopping), because they can be made very thin and with a remarkably sharp edge.
Zirconium oxide, aluminum oxide and other ceramics, in pelletized form, are melted to form this very hard, very dense material. There is no chemical reaction between the blade and acidic or alkaline foods, unlike with steel blades. 
Because of the lightness of ceramics, they do not have the heft you might expect of a metal chef knife, for example. Though not as fragile as one might expect, nevertheless care should be taken not to drop it, to avoid breaking off the tip. Sharpening and repairs are done on diamond hones.

Plastic
With the primary goal of keeping veggies from changing color as they're cut, plastic serrated knives have become more popular of recent. They are not very sharp and some force may be required, so we don't highly recommend them.

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Forged 
This is a process whereby metal is treated, in different steps, to enhance its hardness, density and flexibility. Forged knives are often heavier and better balanced. They are easier to keep sharp, and, with care, can last for generations. You can usually recognize such a knife most easily by the presence of a prominent bolster between handle and blade; a few forged knives are made without a bolster.

Stamped
Such knives are cut or stamped out from flat metal. They do not undergo the steps associated with forging and are thus lighter in weight, are usually not well balanced and not as comfortable in the hand. Because the metal is not as dense as that of forged knives, they don't hold their edge as well. Stamped knives with a high carbon content are usually easier to sharpen and to keep sharp than les expensive knives made of stainless steel with a high chromium content.

Bolster  
An integral part of most good knives, it is a thick piece of metal between the handle and the blade, made to add weight to the knife, provide it with better balance and a comfortable resting place for the hand. It is sometimes called the shank.

Tang
This is the part that runs from the bolster back into the handle. The best knives have a full tang, and, except for some of the sealed-handled knives, it is visible on the top, back and bottom of the handle, held securely by multiple rivets. A half tang is the next preference, visible on top and back of the handle, but not on the bottom.

Handle 
Usually made of wood, plastic, a combination of the two, or metal. The handle envelops the tang, and is usually fastened by rivets or encased in the plastic or metal.
Wood offers an excellent grip but requires regular care; keep it out of water and rub occasionally with mineral oil.
Plastic may become somewhat brittle in time, and can be slippery in the hand.
Plastic-impregnated wood has properties similar to wood, but requires less care and lasts longer.
Some new materials, like polyoxymethylene, offer an excellent grip and comfort, plus they will last almost forever.
Metal lasts longer, adds extra heft, and can be slippery or firm; try them first.
And every manufacturer sports differing sizes and ergonomic designs. A handle that is perpendicular to the blade can be very comfortably used to overcome physical impairments.

Back
Opposite the sharp edge, the back, or spine, is thick on most good knives, except for carvers and slicers, to provide strength to the blade. It can also be used to scrape the cutting board after cutting. Note that, on forged knives, it tapers from the bolster to the tip.

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Flat
This is the wide, flat part of the knife. It can be fully tapered from the back down to the edge, a quality usually found in better knives. In most lesser quality knives, it is hollow-ground to form a distinct inward curve toward the edge. The flat can be useful in crushing things like garlic.

Point 
At the tip of the knife, the point should be sharp and relatively thin. It is used, in many knives, for incisions, for cutting small delicate items and for carving.

Edge 
This sharp part is either flat ground, hollow ground or serrated. In better non-serrated knives you'll find mostly flat ground edges, though a few still sport hollow ground ones with their thinner blade easier to keep sharp.
A good edge is made through a three-step process, ground at three different angles to give them a sharper, longer-lasting edge.