What does the term "permanent wave" refer to in hairstyling?

The term "permanent wave" in hairstyling specifically refers to a method of creating curls that last. This process involves using a chemical solution to break down the hair's natural structure and then reforming it around rods or curlers to achieve the desired curl pattern. Once the chemical treatment is complete, these curls become more durable and can maintain their shape over an extended period, often lasting several weeks or months.

The other options do not accurately represent what a permanent wave entails. For instance, a treatment that straightens the hair involves different techniques, such as relaxers, which aim to smooth and straighten hair rather than creating curls. Additionally, while heat can be involved in the process of creating curls, it is not the only method used; the chemical solution plays a crucial role. Lastly, braiding is a separate hairstyling technique altogether and does not relate to the permanent wave process. This delineation highlights why "a method of creating curls that last" is the correct interpretation of the term "permanent wave."