What technique uses heat to create curls, waves, or straightened hair?

Thermal styling is the correct choice because it specifically involves the use of heat to alter the texture and shape of the hair. This technique is widely employed in various hair services, allowing professionals to create curls, waves, or achieve straightened hair, depending on the tools used—such as curling irons, flat irons, or hot rollers.

In thermal styling, the application of heat changes the hair's hydrogen bonds temporarily, allowing for versatile styling options. This method is suitable for achieving different looks and is a foundational skill in hairdressing and barbering.

In contrast, wet styling involves manipulating the hair while it is damp, using products like gels or mousse to set the style and allowing it to dry naturally. Chemical styling relies on permanent alterations to the hair structure through chemicals to achieve curls or straightening, resulting in longer-lasting effects but not requiring heat during the initial process. Mechanical styling, on the other hand, refers to the use of tools like brushes or combs without the application of heat, thus not fitting the criteria established in the question.