What type of haircut involves very short sides and longer hair on top?

The hairstyle characterized by very short sides and longer hair on top is known as an undercut. This style features a stark contrast between the sharply cropped sides and the significantly longer hair that remains on the crown of the head. The undercut creates a bold and dynamic look, allowing for various styling options for the longer top portion, such as slicking it back, creating volume, or styling it with texture.

While a buzz cut involves clipping the hair very short all over the head, it does not include the longer hair on top that defines an undercut. A fade, although it also has shorter sides, typically blends the lengths gradually instead of leaving a distinct length difference between the sides and the top, which is not the case with an undercut. A layered cut entails cutting the hair at varying lengths to add dimension and volume, typically not differentiating between sides and the top as in an undercut. Thus, the undercut is the correct choice for describing a haircut with very short sides and longer hair on top.