Each game, or “line” of bowling, includes ten turns, or “frames” for the bowler. In each frame, the bowler gets up to two tries to knock down all the pins. If in two tries, he fails to knock them all down, his score for that frame is the total number of pins knocked down in his two tries.
From the spec document:
Each game, or “line” of bowling, includes ten turns, or “frames” for the bowler. In each frame, the bowler gets up to two tries to knock down all the pins. If in two tries, he fails to knock them all down, his score for that frame is the total number of pins knocked down in his two tries.