In Kill la Kill, Life Fibers are an organic cells of extraterraestial origin woven into clothing, which enhances its wearer's abilities to a superhuman degree: They can bestow superhuman strength, speed, agility, resistance to injury, awareness and other superpowers.
One class of such clothing is called "Goku Uniforms" and is divided into three categories based on how much Life Fibers they have woven into them; the more Life Fibers a Goku Uniform contains, the more powerful the wearer becomes at the risk of being overwhelmed, killed and/or consumed by the Life Fibers. A One-Star Goku Uniform has 10% Life Fibers, a Two-Star has 20%, a Three-Star has (most likely) 30%, etc. Clothes made entirely made of Life Fibers are called Kamui and are, at least in Senketsu's case, sentient.