A play action is a play in American football. The attacking team fakes a run game, but actually plays a ball. Play -action is one of the fake moves.
In the typical sequence of a play action the quarterback takes the ball after the snap and runs back to do as if he gives it to the running back. During the transfer, however, he pulls the ball back and hides him in front of the opponent's defense. The running back runs forward, as if he had a ball in his arms and wanted to make amends yards. The Wide Receiver initially work as a blocker to support the fictitious run. So now the opponent's defense focuses on the running back.
Suddenly, however, the quarterback is on the hiding place, breaking wide receiver from their blocks and run free in order to be operated from the quarterback with a pass can.