The stretch of games in Major League baseball that are played from April until the end of September or early October. The regular season consists of around 162 games.
The regular season marks the beginning of official statistics and records that will apply to baseball players' regular career numbers. The season is divided into two "halves", with the All-Star game being played at the midway point of the season. The regular season is when batters build their averages and other batting statistics, pitchers record their ERA, wins and other pitching statistics, and when teams build their win-loss records as they strive to reach the postseason.
For the majority of the regular season, baseball teams have an active roster of 25 players. Beginning on September 1, teams expand their rosters to 40 players. This practice allows teams with injured players to bring more fresh talent up from the minor leagues, relieve stressed and overworked players and injects more competition and excitement into the final stretch before the postseason.