The Corporate Liason is the Weyland-Yutani representative on board the Sulaco. They are NOT a part of the military and are under no obligation to follow military orders - however, they do still have to follow ship-related orders, for example the Commander restricting access to the bridge. The Liason is effectively there only to observe and report back to W-Y the various things that go on during the round.

The Liason doesn't just stop there, however. During the round, they can pray to the admins in order to receive objectives, and the admins are able to spawn "supply packs" that are randomly placed around the station (ie. hidden in various maintenance tunnels). The Liason is NOT able to grief or cause trouble and will be quickly jobbanned if that occurs. They MUST remain in RP at all times.
Think of the Liason like the regular station's Chaplain -- you're a sleazy (or not, if you choose) corporate greaseball who's there to ensure that Weyland-Yutani's assets are being deployed in a financially viable manner, but has no actual authority beyond what their Corporate Overlords (admins) decide.
The Liason gets their own fancy office, which is actually the nicest set of personal quarters on the entire ship. Which is on the brand new bottom deck of the Sulaco. Which I'm not showing yet, haw haw.
Enjoy!