Intrauterine Device (aka "the coil"). It's a physical form of contraception inserted into the uterus. I know more of less how it works but not anything related how it's put there or anything like that. I think what people are saying is that the end of this coil must either press against the bottom of the uterus (to be felt through the wall) or it comes through the cervix and has a physical presence in the vagina? I guess the latter might be how they remove it again... never really thought about it!