Cover
Also said as Hard cover, Half cover, Cover system
Anything that stops bullets and that you can stand behind. Its height and spacing decide the rhythm of a fight: pop out, shoot, get back, move to the next piece.
Without it, a shooter is a contest of who saw whom first. Cover gives the player a place to think and turns a fight into a series of decisions about where to stand next.
Say it
“Space the waist-high cover about 8 m apart, a two-second sprint, so moving up always means a real moment in the open.”
Where you’ve seen it
Gears of War (2006) built its shooting around snapping into cover and sprinting between pieces of it, and a generation of third-person shooters copied the idea.
Not to be confused with concealment
Concealment hides you and cover protects you. Tall grass hides you and stops nothing, which is a fine thing to make a player learn the hard way.