There are two kinds of suture: absorbable and non-absorbable.
These break down in the body and are often used internally. Absorbable sutures include chromic/plain gut, monofyl/Monocryl®, PDO/PDS, and PGA/Vicryl®.
These must be manually removed and are often used externally. Non-absorbable sutures include nylon, PGA/Vicryl®, silk, polyester, and stainless steel.
Each type of suture can also be classified by their type: monofilament or multifilament. Monofilament suture includes: polypropylene, gut, nylon, stainless steel, etc. These provide the better passage through tissue, giving a lower tissue reaction. Multifilament sutures include PGA, polyglactin, silk, and polyester. Multifilament sutures are braided and may be coated with silicone, wax, etc. This type provides better knot security over monofilament.