Batting Cages

The player currently batting in a game is said to be at the plate, at bat, or up to bat (shortened to up)

To keep the game moving at an orderly pace, the attached batter due up waits to take his circumvolution in a circle (actually considerable or imaginary) between his team's dugout or bench and the batter's box, and is said to be on deck, with the http://www.pitchingmachines.net/Batting-Cages-s/24.htm circle known as the on deck circle
The player in the batting lineup after the on deck batter is said to be in the hole.

The defense attempts to get the batter out. The pitcher's main role in this is to throw the ball in such a expedient that he or she either strikes out or cannot hit it cleanly so that the defense can get him or her out.