Rewards can be anything players earn via game play. Some games have them. Many games don’t. The new wave in learning games—and in gamification of learning—is to give players achievements for accomplishing certain tasks or hitting certain milestones.
A game’s mechanics are the rules and procedures that guide the player and the game response to the player’s moves or actions. Through the mechanics you create, you define how the game is going to work for the people who play it.