A medal is an award for some contest or achievement. You might win a medal for coming in third place at the cupcake baking championship.
A medal is often a flat piece of metal that's stamped with an inscription or design and is given in honor of winning a race, serving in battle, or another remarkable accomplishment. Scholars, athletes, and soldiers all might win medals. Originally, a medal was a "trinket," and it wasn't until the 18th century that it began to mean "reward for merit."