A calf support or heat retainer provides protection and support. It retains the heat produced by the body in a specific area and so aids healing. Heat encourages blood vessels to dilate and so allows more blood to the injured area. The more blood that gets to the injured area, the more nutrients it will get and the faster it will heal.
Use it for helping to get better but do not rely on it indefinitely. If you find you need to wear it for more than a week then you really need professional help.