Anything motivational makes you want to do something — or at least be willing to do it. When you're training your dog, the treats in your pocket can be used as motivational tools.
If someone gives a motivational speech, their purpose is to try to get people excited about doing or trying something. A football coach's motivational talk to his team, for example, is intended to inspire the players to win the game. In other words, what the coach says motivates the team to play well. Both motivate and motivational come from the Old French motif, "drive or motivation," from motivus, "moving" in Medieval Latin.