Doctors prescribe medicine to eliminate disease from the body.
The Teachings of the Buddha are perscribed to cure disease of the mind, to bring back its natural healthy state. So Buddha can be considered to be a doctor who prescribes cures for the ills of the mind. Wrong Understanding which lets Greed, Hatred and Delusion take over the mind. But in truth these things are not the essence of Buddhism. That's what is called Dhamma and that's what should be studied throughout our daily lives so that when some mental impression arises in us, we'll be able to deal with it and go beyond it.