What Is a Bunker in Golf?

Answer:

A bunker is a hazard consisting of a prepared area of ground, often a hollow, from which turf or soil has been removed and replaced with sand or the like.

Grass-covered ground bordering or within a bunker is not part of the bunker.

The margin of a bunker extends vertically downwards, but not upwards. A ball is in a bunker when it lies in or any part of it touches the bunker.