A laurel is a wreath worn on the head, usually as a symbol of victory. If you see an image of Julius Caesar, chances are he's wearing a laurel.
A laurel is a type of wreath — circular, made from leaves and branches — worn on the head in ancient times. The laurel is a symbol of victory that lives on in the phrase "Resting on one's laurels." When you rest on your laurels, you're happy with previous successes but not doing much to continue succeeding. You've gotten lazy and complacent.