I recently bought carpet for a townhouse, and it is indeed a daunting experience. However, I'll try to make your carpet buying experience easier. Carpet fibers are made from natural materials such as wool or silk, and from man-made materials such as nylon, polyester, and polypropylene or olefin. Wool or silk carpets are specialty items. Commercial carpets are made from the man-made fibers which can even be blended together.
Carpets have different textures depending on how the fibers are woven.
Common examples of textures are twist, shag, and velvet. A Berber or loop texture is often used in recreation rooms. The stain resistance of a carpet is the result of the combination of fiber and treatment. Stain resistant materials can be bonded to the fibers at the factory, or applied to the finished carpet. Bonding stain resistant materials at the factory is much more expensive than applying them to the whole carpet.