Heel spurs are growths of bone on the underside, forepart of the heel bone. Heel spurs occur when the plantar tendon pulls at its attachment to the heel bone. This area of the heel can later calcify to form a spur. With proper warm-up and the use of appropriate athletic shoes, strain to the ligament can be reduced.
If you have pain in your heels that isn't going away, you should see a podiatrist. The longer you wait to be treated, the longer your healing process. Treatment can usually be nonivasive and painless if it is caught in the early stages.