A quarter is a segment of a football game, of which there are four in every game. In the NFL, each quarter is fifteen minutes long. Other levels of competition have different quarter lengths, but most all levels use the four-quarter segmentation model. Between the first and second, and third and fourth quarters, there is a short break for each team. There is a longer break in the middle of the game, between the second and third quarters; this is known as halftime.
In the NFL, teams switch sides after each quarter. This ensures no team has an advantage by playing towards one side of the field. The actual length in real time of a quarter is often much longer than fifteen minutes. This is because the clock is stopped at specific times during the quarter, such as after an incomplete pass or a timeout by one team. If a game is tied at the end of four quarters, an overtime quarter is played.