Facehugger

A facehugger is the initial form of the Alien Xenomorph creatures from the Alien movies and games. When a facehugger emerges from an egg laid by a queen, its goal is similar to a headcrab (from the Half Life-series) but more parasitic. Once a facehugger attaches onto, or facehugs, a host, it inserts an alien fetus into the chest through a mouthpiece extended from the facehugger. It then acts as a parasite. Later, the alien emerges from the chest as a chestburster, thus killing the host. The chestburster is very weak, but it hides and eats, eventually becoming a Drone, Runner or Predalien (A hybrid Predator and Alien). One chestburster eventually becomes a queen which lays more eggs. The queen is also guarded by Warrior aliens, made by the Superfacehugger. Like most Xenomorph forms, facehuggers have acidic blood.

Superfacehugger
The Superfacehugger, sometimes called the Queen Facehugger, is a different type of Facehugger. The Superfacehugger has a black exoskeleton (similar to the adult form of the Xenomorph,) a spiked tail, webbing between its crablike legs, and it carries either one Queen embryo, or a Queen embryo and a normal Xenomorph embyro (according to popular fan theories.) The Superfacehugger is seen only in the Special Edition of Alien3, and is often considered canon. Aside from those differences, the Superfacehugger is no different from the normal Facehugger.