Which tool is essential for a barber when performing haircuts?

Barber shears or clippers are essential tools for a barber when performing haircuts due to their primary function in cutting hair. Shears are specifically designed for precision cutting, allowing barbers to create various hairstyles, textures, and layers. Clippers, on the other hand, are invaluable for achieving uniform lengths and are often used for buzz cuts and fades. The use of these tools ensures that barbers can provide professional and tailored haircuts that meet their clients' desires.

While the other tools listed, such as a hairbrush, hairdryer, and comb, are useful in the overall hairstyling process, they do not serve the fundamental purpose of cutting hair. A hairbrush is typically used for smoothing and styling, a hairdryer is for drying, and a comb is often used for sectioning or managing hair during the cutting process, but they are not the primary cutting instruments. Thus, barber shears or clippers stand out as the essential tools without which haircuts cannot be effectively performed.