Definition of a mirror game?

[Kelen]

Can someone please clarify something for me. What exactly is a 'mirror game'?

I recently agreed to my first ever 'mirror' game, only my understanding of what they were appears to have been incorrect.

I assumed a mirror game was exactly that, that is one map 2 games, one you play Allies, one Axis. Whilst I am indeed playing 2 games, (1 Allied, 1 Axis), they are using different maps, and in both I'm attacking and my opponent defending.

Whilst I don't necessarily mind that, I would like to know for future reference so that If I invite, or am invited to play any more, both my opponent and I know what to expect; or if both options are valid that I need to be clear and what the exact arrangement is.