Calf is the back portion of your lower leg, it on the backside of your leg. Start from the backside of your knee and ends to your Achilles tendon. There are two muscles in calf the gastrocnemius and soleus. The main function of the calf muscles is to extend your foot from the ankle and flex your toes. The main use of the muscle is when you are running, walking or jumping.
There are few exercises to work out your calves. The main thing in these exercises is to do the repetitions in controlled manner and with relatively slow speed. Use almost the full range of motion when doing the exercises! This will ensure that your calves get a good workout.