What defines a chemical relaxer?

A chemical relaxer is specifically designed to alter the structure of curly or wavy hair, enabling it to be straighter and more manageable. This is accomplished through chemical processes that break down the bonds in the hair's cortex, allowing the natural curl pattern to be loosened or eliminated.

The key distinguishing characteristic of a chemical relaxer is its primary function of straightening hair, which aligns well with the definition provided in the correct choice. Other options focus on aspects that are not related to the intended purpose of a chemical relaxer. For example, a product that lightens hair relates to coloring, while a method to curl hair pertains to processes that create waves or curls, which is the opposite of what a relaxer does. Lastly, a treatment for damaged hair refers to restorative products rather than straightening ones. Thus, the role of a chemical relaxer is clear and specifically effective in achieving a straightened hair texture.