Carpeting is one of the biggest investments you're going to make when furnishing your home [source: Carpet Buying Guide]. Carpets can be made of many different types of fibers.
Nylon is the most popular carpet fiber. It's durable, fairly stain-resistant and easily cleaned. It is also moderately resistant to fading, though it will fade if it is exposed to the sun for long periods. Nylon is moderately priced. Extra-soft nylon has thinner strands and is therefore plusher, but it might not be quite as strong as less luxurious alternatives.
Polyester is one of the cheapest carpet fibers available. It is stain-resistant and won't fade in the sun, but it lacks durability. There is a new version of polyester, Polyethylene Terephthalate (PET), which is sturdier than its predecessors. Polyester carpeting is good for people who suffer from allergies because it resists mildew and sheds water.
Wool is considered to be the highest-quality fiber for carpeting because of the way it looks and feels, but it is also fairly expensive. Although wool comes in rich colors, it does fade when exposed to direct sunlight. It's not resistant to mildew or mold and it wears down relatively easily.
Acryliclooks and feels a lot like wool; however, it tends to fuzz and pill, and it's more expensive than some of the other synthetic choices.
Olefin, also called polypropylene, is resistant to mildew, moisture, static and stains (except oily ones). Because olefin fiber wicks away moisture, it's good for outdoor areas and damp basements. It can be chemically treated so it won't fade, but although it's pretty durable, it's neither as resilient nor as soft as other carpet fiber options.
If you want to be a "green" shopper or homeowner, you might want to consider nylon or polyester carpets, which can be made from recycled materials.