what happens in an mmorts when you log off?

Exactly what it says on the tin.

I was looking at games like Evony, which state that stuff keeps happening when youre logged off, including resource gathering and "ingame" events. Can you be attacked while youre logged off? How could you defend yourself effectively?

Mmorts? Oh, Massively Multiplayer Online Real Time Strategy.

I'd guess you wouldn't be able to be attacked for sake of fairness.

I was wondering how that will work in Age Of Empires online.

Hmmm. Speaking for MMORPG's, I can imagine that my character was complaining as to why I hadn't had the decency to log him out in a comfy chair or at the very least, indoors. Being stuck outside when a sandstorm hits on Tatooine sucks, yo.

It probably depends on the game, no? But, for the one I played briefly, the time scale was deliberately slowed (constructing a ship took realtime minutes or hours, that sort of thing) so that you wouldn't miss much.

This. Most MMORTS games aren't RTS in the sense of "command and control in real time" but in the sense of "order an attack and it will take 5 real-time hours to hit the target". There's usually some kind of scouting mechanic as well so as long as you log on a few times a day you usually have a chance to react before stuff hits.

The thing is, Age Of Empires Online will have real time combat.

Well, the questions been mostly answered. But: I'd recommend against playing Evony. It installs spyware.

And it has stoopid ads.

And the game itself is LAME, to a scale of about 63 centifarmvilles.