You have 2 major calf muscles, the gastrocnemius and soleus. The bigger and closer to the skin, your gastrocnemius, propels you as you run. When you are standing upright, that’s your soleus.
Try calf raises: stand on your tiptoes, then lower; tiptoes, then lower. Those are your calf muscles lifting you up.
-Diaz, Cameron. The Body Book: The Law of Hunger, the Science of Strength, and Other Ways to Love Your Amazing Body. N.p.: HarperCollins, n.d. Print.