What does the ~ in front of the digital pins mean?

Hi everybody,

I'm new to electronics, and I recently bought a Arduino uno. I noticed that some of the digital pins (0-13) have a ~ in front of them, and some don't. I thought '~' meant alternating current. Does this mean that some of the pins have alternating current and some have direct current? (somehow that doesn't seem very likely)

Kind regards,

Thanks!!