Don't let it scare you. It never realy comes up. So there it is. All rooms connect and are laid out in a fixed way. That's one key.
All music is a twelve storey apartment block, twelve floors of identical layout.
The Music Building. So, each key consists of seven chords, laid out identically. If you know one, you know 'em all. The One chord will always be the living room, the Six chord, always the kitchen etc. etc. There aren't that many.