Backcombing (teasing) is used to:

Backcombing, also called teasing, involves combing shorter hairs back toward the scalp to add volume, fullness, and support to a style. It is a temporary, physical styling technique. Done gently and removed carefully afterward, it helps build height and structure in updos and voluminous styles; done too aggressively, it can tangle and damage hair. Understanding common styling techniques like backcombing — and that they are temporary physical effects — is part of the hairstyling content covered on the exam.