A scalar value which represents the degree to which a state or action is desirable. Reward functions can be used to specify a wide range of planning goals (e.g. by penalizing every non-goal state, an agent can be guided towards learning the fastest route to the final state).
Something God gives to those who please Him. In the broadest sense, a reward is whatever we receive for our actions, good or bad. We cannot earn our salvation, which is a gift from God (Romans 6:23), yet Christ shows through the parable of the talents that some will receive greater rewards than others in the Kingdom of God because of their service to their Creator (Matthew 25:14-30). The righteous reap their ultimate reward at the time of the resurrection of the just.