The purpose of fabric softener is to soften fabrics and prevent static cling. Softener chemicals adhere to the fabrics, giving them a softer feel. Some people use scented softeners for a pleasant smell.
Fabric softener is commonly added in liquid form to clothes in a washing machine, although a newer form of softener is made from crystals that are put into the washing machine. Fabric softener sheets are another product used during the drying cycle to soften clothes. Some people add fabric softener to all washing loads, but Good Housekeeping points out that it isn't good for certain materials, such as towels and micro-fiber.