Work is the transfer of energy. In physics we say that work is done on an object when you transfer energy to that object. For introductory thinking, this is the best definition of work.
If you put energy into an object, then you do work on that object.
If a first object is the agent that gives energy to a second object, then the first object does work on the second object. The energy goes from the first object into the second object. At first we will say that if an object is standing still, and you get it moving, then you have put energy into that object.
For example, a golfer uses a club and gets a stationary golf ball moving when he or she hits the ball. The club does work on the golf ball as it strikes the ball. Energy leaves the club and enters the ball. This is a transfer of energy. Thus, we say that the club did work on the ball.
And, before the ball was struck, the golfer did work on the club. The club was initially standing still, and the golfer got it moving when he or she swung the club.
