Also question is, where did the Xenomorph Queen come from?
As far as I know, there is no officially canon answer for how the queen in Aliens got there. However, there are two ways a queen can come about - either from super/royal facehuggers (shown in the Director's Cut of Alien 3) or from molting (shown in the Alien vs. Predator (2010) video game).
Subsequently, question is, what is a Xenomorph Queen? A Queen is a huge Xenomorph that serves as the mother and leader of a Xenomorph hive. Her appearance differs from that of a drone, with a pair of extra arms and a large head crest. Individual Alien Queens vary in size, age, and appearance.
Similarly, what is a Xenomorph egg?
The Egg is the first stage of the Xenomorph's life cycle, it serves as an organic capsule for the facehugger. They can be produced by cocooning a living host. The large Queen alien can produce hundreds of eggs at a rapid rate, through the use of its ovipositor.
Why does the Xenomorph have two mouths?
In the Biology Section it points out that the "tongue mouth" or secondary jaws (or mouth) is what the Xenomorph eats with. It can't easily swallow, so it grabs prey and the smaller internal jaws, the pharyngeal jaw, then bit and pull the food into the gullet.
