Are Tesla superchargers free?

I've been considering purchasing a Tesla and I've heard a lot about their supercharging stations. Can you tell me, are Tesla superchargers free to use? I'm trying to factor in the cost of owning an electric vehicle and want to make sure I understand all the expenses involved. Additionally, are there any limitations or restrictions on using the superchargers that I should be aware of? I'm excited about the potential of electric cars but want to make sure I'm making an informed decision.