In the movie Aliens (1986), the following exchange occurs as the marines are on route to the stricken colony:
Hudson: Is this gonna be a standup fight, sir, or another bughunt?
Gorman: All we know is that there's still no contact with the colony, and that a xenomorph may be involved.
Frost: Excuse me sir, a-a what?
Gorman: A xenomorph.
Hicks: It's a bughunt.
I know that xenomorph is the name given to the Alien species in the franchise, which would mean that at the very least Gorman knows about them. Yet as the subsequent events show, the marines have no idea what they are in for, and are taken by complete surprise.
So what are the xenomorphs Gorman is talking about? And what "bugs" are they talking about hunting?