Twill is a weave of fabric that is known for its durability and ability to drape well. The easiest way to identify twill is by its diagonal pattern that can be seen in the cloth stitching. Common types of twill woven fabric are denim, chino, tweed and gabardine.
Unlike simple plain weave fabrics which are uniform on both sides, twill weaves have a distinct front and back side; each with their own characteristics. The front side of twill is generally more durable and clean looking than the back side; as such when garments are created they almost always have the front side of twill facing out. The front side of twill also has a more textured surface than the back side; and it is for this reason that twill woven cloths are not considered suitable for printing.
Because twill weaves allow for the threads to skip over each other in groups of two or more the fabric moves more freely than plane woven fabrics. This free movement results in a softer fabric, and one that resists wrinkles better. Additionally since twill allows for larger groups of threads to be skipped over it is possible to manufacture twill cloth with higher thread counts, which in turn leads to more durable fabrics.