Hitbox

Hitboxes of a Combine

A hitbox is an invisible box (or more often a series of boxes) which define the rough shape of a model for purposes of damage-based collision detection. A typical model within a game is much too high-poly to perform real-time hit calculations on, so hitboxes are used instead.

A hitbox is different from a bounding box in that it is more complex and closer to the model's visible shape. The bounding box is used for movement-based collision detection, and is usually literally a single box. There is a way to 'delete' the Hitboxes by setting yourself Solid 0, but there will be still some hitboxes.