A hair perm, short for permanent wave, is a chemical treatment that alters the structure of hair to create curls or waves. This process involves applying a perm solution that breaks down the hair's protein structure, followed by wrapping the hair around rods to shape it. After a set period, a neutralizer is applied to lock in the new shape, resulting in long-lasting curls. Perms can vary in size and tightness, allowing for different styles, from loose waves to tight curls. While the effects can last several months, proper care is essential to maintain the health of the hair and the longevity of the perm.