I KNOW there will be at least a few who make fun of me for asking this question, but I'm going to anyway

I've only ever seen Yorkies with docked tails. My Baxter's tail is short. What exactly is docked-I think you have to actually do this to the tail...

It doesn't grow back, does it? The reason I ask is because I just saw a couple of pictures of Yorkies and they had long tails.