It's a viral infection, so it can be contagious. I had several of them in my teenage. It started from one hand, and then to another hand, from 1 to 3-4, I remember. That's because I keep touching it. None of my family members had them, no one touched my hands so no one got it from me. The virus can exist anywhere, you touch it, it came to you. Many people contact the virus, only a very small portion of people had it. Plantar warts look quite special, find some pictures of them, then you'll be able to identify them.