Re: difference between work done by the bodyand work done on
It's easier to think in term of energy, since work is really energy: if you do work to the body, it accumulates energy, whereas if the body does work, it loses some energy.
Think about lifting a body: its potential energy increases, so you did work to the body. But if it falls, then it loses its energy, doing work, and it dissipates that energy either by heat as it hits the ground or gives it to another body that it strikes.