The two minute warning acts like a timeout. The game clock stops ticking when the clock hits 2:00, unless there is already a play going on. If a play is ongoing when the clock hits 2:00, it will continue running but will stop at the next stoppage in play. The 2 minute warning does not count towards a team's timeout limit.
The 2 minute warning only happens when there are two minutes or less left in the second quarter and fourth quarter. Only the NFL has the two minute warning. There is no two minute warning in college football or in high school football.
If a team is trying to preserve time on the clock, they can use the 2 minute warning to their advantage. Teams may be trying to preserve time at the end of the second or fourth quarter for one of the following reasons:
Since the 2 minute warning has the same clock stopping ability as a timeout, it is helpful for a team making a last second push. Normally a hurry-up offense has to worry about getting out of bounds to stop the clock. However, if the 2 minute warning is approaching they can afford to get tackled because the 2 minute warning will stop the clock.
It is important not to waste a timeout when the 2 minute warning stops the clock. This would be pointless, as timeouts are typically used to stop the clock from running.
When the clock hits two minutes, every scenario will stop the clock, like any ball that goes out of bounds or any dead ball on the field. The two minute warning only exists in the NFL. If the ball is live when the clock hits the 2 minute mark, the officials will announce the 2 minute warning after the play is concluded and the ball is dead.
When the 2 minute warning hits, it can be a wake up call for the players on the field! The losing team knows that it's crunch time and there isn't much time left to make a comeback. The 2 minute warning is a nerve wracking time for both teams, coaches and all fans, because the course of the game (and the winner) could change in a matter of seconds.