i think it means get root user, sort of a super user, permissions for your phone - so you/apps can do more stuff on it - its good to have when you are flashing roms etc
....but i will let SU tell you more, maybe
Have a read of this sticky, explains it pretty well
what does pulling root mean?
Pulling root isn't a term I'm familiar with
Pulling root might be a slang for unrooting, but I've never heard it either.....
I think that is something your Dentist does!