Final answer:
A trimmer, or edger, is used to outline and refine the hairline, giving a precise edge to a haircut. It is distinct from depilation methods as it is used for styling rather than removing hair.
Step-by-step explanation:
A trimmer, also known as an edger, is a tool commonly used in cosmetology. It is designed for outline and refine the hairline. This tool helps in cleaning up the edges around the ears, back of the neck, and sideburns to give a sharp and precise finish to a haircut. Trimmers can also be used to create artistic designs or patterns in the hair. In contrast to depilation, which involves removing hair above the skin's surface such as shaving or using chemical depilatories to break disulfide bonds in hair, trimmers are typically used for styling rather than complete removal of hair.