Basically, it is bunch of players running pieces of one empire together. A little big like AI ministers, with more focus on controlling territory than empire-wide functions.
Everybody posts orders for the stuff they own into the forum, and I do the grunt work of merging and typing it all in before posting the results for the next turn.
See here:
http://www.shrapnelcommunity.com/thr...b=5&o=&fpart=1
And here:
http://www.spaceempires.net/home/forum-c13.html