There are 2 main muscles that compose the calf: Gastrocnemius and Soleus. Together these 2 muscles work to contract and relax in order to create movement. Not only are these muscles related to your lower leg, but as you will see below, they also attach to the Achillies tendon which runs into the back of the foot and ankle.
Sometimes a simple stretch may help to ease some of the pain and even stop a cramp from happening, however if the muscle is in need of relief consult your myotherapist.
Below is a video that demonstrates some stretches you can use to help calf pain.