A game of bowling consists of 10 frames You have 2 chances per frame to knock down all the pins. The total after the 2 balls is your score unless you get a strike (Knocking down all the pins on your 1st ball) or a spare. Example below: the 1st ball knocked over 4 pins, the second ball knocked over 5 more pins so the score for that frame would be a total of 9.
If you knock down all the pins on your 1st ball it is considered a strike and is counted as 10 plus your next 2 balls thrown.
If you knock down all the pins using your 1st and 2nd ball, it is considered a spare and is counted as 10 plus you next ball.
If you get a spare in the 10th frame, you get 1 more ball If you get a strike in the 10th frame, you get 2 more balls