An inning in baseball is a structure of a baseball game is made up of these. Each one has a top half and a bottom half, each comprised of three outs being made. In each half-inning, teams take turns playing offense and defense. The away team always bats first at the top of the inning, while the home team bats second at the bottom of the inning. The middle of the inning refers to the time in between half-innings, in which teams switch roles on the field.