A manager in baseball is someone on the team responsible for the operation of a team, including player contracts, and hiring and firing of a field manager and other personnel.
Each team has a manager who acts as a head coach. He makes important strategic decisions before and during the game, such as the batting order (the order in which batters in the game will bat) and which defensive position each player will have for the game. Before the game, he creates a lineup card, which lists the batting order and the defensive position for each player. He then presents it to viewers and the umpire.
A manager who makes decisions such as who plays what position on the field and when they bat in the batting-order controls every baseball team. Each club designates a manager to the league president or umpire-in-chief before the game begins.