At its core, the xenomorph is a hostile parasitic pathogen (Chemical A0-3959X.91) whose mutable mechanisms are signaled by perturbances to its chemistry. It evolves to assume biological and physiological traits of its host, thereby enabling it to adapt to its environment.
Here is a comprehensive list of all Xenomorph types from the Alien movies and beyond, including the facehugger, chestburster, warrior, and Queen Xenomorph variants. The Xenomorph appearances and behavior vary based on the type of the host but also in the placement of the creatures in the Alien lifecycle.
A xenomorph is a type of alien from the science-fiction horror franchise Alien known for its grotesque appearance and parasitic form of reproduction.