What it is

Running out the clock means using up time on purpose, usually with running plays, so the other team gets less time to come back.

In a game

The offense stays inbounds, keeps the ball safe and takes as long as it can between plays, using the play clock.

More detail

The final step is the kneel, which ends the game without any risk. A team that cannot gain yards can still use the clock if it gets a first down.