Primary Reinforcer: This is something necessary for survival, such as food or water. In our arcade analogy, this would be like needing tokens to play the games.
Secondary Reinforcer: These are learned value items, such as money or grades in school. In our arcade analogy, these would be the prizes you can win with your tokens.
Conditioned Reinforcer: This is a stimulus that has become rewarding by being paired with another reinforcing stimulus. For example, if every time you won at an arcade game you also got praise from your friends (another reinforcing stimulus), winning at the game might become rewarding in itself.