There are three styles of WC’s Close Coupled, Back-to-wall and Wall Hung.
A close coupled cistern is a type of toilet where the cistern itself is mounted directly on top of the toilet bowl, so that the toilet is one complete unit.
The cistern (sold separately) is hidden behind the toilet pan, either within a toilet unit or concealed by a stud wall.
A wall hung toilet is hung on a concealed frame, allowing a tiled floor to be fitted flush to the wall. The cistern is concealed within a toilet unit or behind a wall.