A game that has gone far enough to be an official game, and ends with a tie score. Tie games do not count in standings, but statistics from such games are counted in player and team stats. (Obviously, there is no winning or losing pitcher.)
20th-century MLB rules required that tie games be replayed from the beginning. This is why you will sometimes see, in season team stats from that era, that a team played more than the scheduled number of games. Replays of tie games were more tolerable in the days when the regular season schedule was 156 games, and the postseason consisted only of the World Series. But after the schedule expanded to 162 games, and rounds were added to the postseason (crowding the regular season and reducing days off for teams), replaying tie games started to cause scheduling difficulties and additional burdens on teams. Under current rules, an official tie game can only occur if a game is suspended with a tie score, and then not resumed before the season ends.