I have a weird callus at the bottom of each foot. What is it?

I have them too! Had them for years. They are called Plantar Warts. I keep shaving them down. I try everything but they are always there. They hurt when they grow alot, right? My podiatrist said there is nothing you can do except keep going to him and he shaves them down. Gets expensive but don't get a razor blade and try it yourself, I cut myself badly once trying that. What do you do for them?