Props spin either clockwise (standard or right-hand rotation) or counter-clockwise (counter or left-hand rotation).
Most single engines use a standard rotation prop. Most twin engines use one of each. To determine what prop rotation you have, look at your prop as if on a boat. Position a blade pointing straight up. If the right-hand side of the blade is closer to the boat than to you, it's a standard rotation prop.
Rotation on Twin Engines
Two propellers spinning the same direction on twin engine boats will create steering torque. In other words, two right-hand (or standard rotation) propellers pull the stern hard to the right and the bow to the left.
Two opposite-direction propellers on twin engines eliminate this steering torque because the left-hand (or counter rotation) propeller balances out the right-hand propeller. This results in better straight-Line tracking and helm control at high speed.
Opposite-direction propellers on twin engines eliminate steering torque because the left-hand prop balances out the right-hand propeller.