As Ms Swetha said, reward is a positive term and compensation is a negative term. When we say reward, we feel happy as it accompanies a happier event / contribution. At the same time, when we say compensation, it follows a negative (exhausted labor to compensate) or not more happier contribution. Moreover, the term "reward" is used for payments at will; but the term "compensation" for legal payments. I mean, in legal parlance, the term "compensation" is appropriate than reward.