Hair curlers are styling tools used to create curls and waves in the hair. The most common types of hair curlers are perms, rollers, and irons. A perm is a chemical treatment that permanently changes the structure of the hair, creating curls or waves. Rollers are small cylinders that are rolled into the hair and then heated to create curls. An IRON is a flat metal tool that is heated and then used to wrap sections of hair around it to create curls.