Overtime is the name for the extra portion of a game in the case of the two teams having a tied score at the end of regulation in football, basketball, and hockey; though baseball uses the same concept, it is more commonly referred to in that sport as "extra innings".
In the case of two teams tying at the end of the fourth quarter, the two teams will play an overtime period. Similar to the beginning of the game, there will be a coin toss, with the winning team selecting whether to kick or receive the ball. The first person to score in the overtime period is declared the winner. In a regular season or preseason game, if neither of the teams scores by the end of the game, the game is ruled as a draw.
In basketball, the two teams will play another five-minute quarter. At the end of this quarter, the team with the higher score is declared the winner. If the score is still tied, the game will go to a second overtime, and so on until a winner is decided.
In hockey, the two teams will play one final timed period. The first team to score in that period is declared the winner. If neither team scores by the end of the period, the game will be decided in a shootout.
In baseball, two teams will continue to play in extra innnings, starting with the tenth inning and continuing until one team has the lead after the bottom of an inning. The most well-known game in recent history to be declared a draw was the 2002 MLB All-Star Game, after both teams had run out of pitchers in the eleventh inning.