Types of Cotton
Why the type of cotton in your sheets, bedding and towels matters:
Cotton is the most widely used fiber for fabric because of its
strength, durability and breathability. The word "staple" refers to
fiber length. When someone refers to "long staple cotton" they are
referring to variety 1, 2, or 3. The longer the fiber size of a
variety, the more difficult it is to grow, and the more difficult it is
to process. Hence the longer the staple, the more expensive it becomes.
(The image below shows the approximate relative sizes of the fibers.)
1. Sea Island Cotton
Sea Island Cotton is in extremely limited supply, and is very expensive
to grow and to process. It is typically used in very expensive men's
shirts.
2. Egyptian Cotton
Egyptian Cotton was developed from stocks that originated in South and
Central America. Menoufi is the most widely used variety. However, just because it is grown in Egypt, it doesn't mean it is the best cotton. There are many varieties of Egyptian Cotton, and they are all graded by quality. The highly
prized Giza cotton variety has exceptionally strong fibers about 1½" long, and
is used in the best qualities of embroidery thread, and the finest
cotton fabrics for sheets, down bedding covers, and duvet tickings. Learn more about Egyptian Cotton

3. Pima Cotton and Supima Cotton
Pima cotton is generally in-between Egyptian Cotton and American Upland long staple in length and price. It is usually a good quality. However, Pima cotton is a generic term and does not mean it is made with extra long staple cotton. What you really want to look for to ensure a quality sheeting is Supima Cotton, this is a trademark for American grown, extra long staple cotton. Generally Supima cotton is grown only in Arizona, Texas, California and New Mexico and has a strict supply chain to ensure quality. Supima cotton represents less than 1% of all cotton grown in the world.
4. American Upland Long Staple Cotton
This cotton is only "Long Staple" in comparison to American Upland
Short Staple cotton. The American Upland cottons now comprise up to 90%
of the worlds crop. They are much easier to grow and process, and are
therefore much less costly. They are perfectly adequate for medium
quality fabrics. They make poor downproof fabrics for duvets and
pillows, as they will ultimately leak. They are also unsuitable for
high thread count sheets, as they will feel limp and coarse after a few
launderings. This is the cotton used in bargain duvets, and in
inexpensive "luxury" sheets.
5. American Upland Short Staple Cotton
A less expensive version of cotton, and a very basic quality. Suitable for denim for blue jeans.
6. Asia Short Staple Cotton
Asia Short staple is very easy to grow and process, and hence makes
very cheap cloth. Unfortunately, lightweight fabrics made from this
cotton are very weak and limp. They wear out quickly, and launder
poorly.