Hitbox
An invisible shape attached to a game object that decides what counts as a hit — rarely the same thing as the image you see.
Fighting games separate the hitbox (an attack's damaging region) from the hurtbox (the vulnerable region); a blow lands when one overlaps the other. Decoupling the shape from the sprite is the whole point — that is where the designer dials in feel.
Generous hitboxes forgive sloppiness, tight ones punish it, and an invisible hitbox can reach further than the sword appears to. The approach is both simpler and far cheaper than pixel-perfect collision, and it has shaped how games feel since the arcade era.