Ripley: Micro changes in air density, my ass.
Parker: It's a robot. Ash is a god damn robot.
Ripley: Ash, can you hear me? Ash!
Ash: Yes, I can hear you.
Ripley: What was your special order?
Ash: You read it. I thought it was clear.
Ripley: What was it?
Ash: Bring back lifeform: Priority One. All other priorities rescinded.
Parker: The damn Company! What about our lives, you son of a bitch?
Ash: I repeat: all other priorities are rescinded.
Ripley: How do we kill it, Ash? There's got to be a way of killing it. How...how do we do it?
Ash: You can't.
Parker: That's bullshit!
Ash: You still don't understand what you're dealing with, do you? The perfect organism. Its structural perfection is matched only by its hostility.
Lambert: You admire it.
Ash: I admire its purity: survival unclouded by conscience, remorse or delusions of morality.
Parker: Look, I've heard enough of this and I'm asking you to pull the plug.
Ash: Last word.
Ripley: What?
Ash: I can't lie to you about your chances, but you have my sympathies.
Ripley: Ash, that transmission... Mother's deciphered part of it. It doesn't look like an S.O.S.
Ash: What is it, then?
Ripley: Well, I... It looks like a warning. I'm gonna go out after them.
Ash: What's the point? I mean by the, the time it takes to get there, you'll... They'll know if it's a warning or not, yes?
Answer: It's another race of space alien that is also subject to infection by the Aliens. This particular one was infected and moved as far as it could from its race's known space and broadcast a warning before it died. The presence of eggs in the hold may indicate that it was a research ship. The race was never used in other Alien movies because it adds a new dynamic to the plotlines: two alien species, locked in mortal combat and neither particularly friendly with humans. In the Alien pseudo-prequel Prometheus we learn these beings are known as the Engineers and have interesting ties with both the aliens and humans as well.
Phoenix