An Intrauterine Device (IUD) is a small, T-shaped device inserted into the uterus to prevent pregnancy. It can be made of plastic or copper and works by either releasing hormones or creating a hostile environment for sperm. IUDs are highly effective, with a success rate of over 99%, and can last several years, depending on the type. There are two main types of IUDs: hormonal and copper. Hormonal IUDs release progestin, which thickens cervical mucus and thins the uterine lining. Copper IUDs use copper to deter sperm. Both types are reversible, allowing for fertility to return quickly after removal.