The alien organism hits the glass with a loud thud and starts to suck the glass surface as it tries to reach Burkes face. A rattling is heard as the parasite springs to live with excitement. A face hugger is a parasitoid that's only purpose is to make contact with a hosts mouth so that it can implant eggs (Oviposito) into a victims esophagus,  The eight fingers are used to securely tighten it's grip around the face of the host so that it is almost impossible to remove unless massive injury is caused or in most cases death. The tail of the facehugger will tighten around the victims throat if it feels endangered or threatened, The alien organism supplies oxygen to the victim by two lung like organs that are attached at each side, but the victim will be comatosed during this stage and will only feel better after the stage of embryonic implantation has completed. The alien hosts epidermis solidifies into a chitinous layer of silicon possibly to ensure the success of the implantation, the parasite will detach from the host and retreat to die once the stages are complete.
A face hugger is the second stage in the life cycle of a xenomorph it comes from an egg. Face huggers are very athletic and can launch and pounce from great distances, they are also great hiders and like to strike when the victim is completely unaware. Surgical operations to remove the parasite result in a highly pressurized molecular acidic blood which will spray wildly if the parasites skin is cut, This would kill the host from severe burns at acts as an excellent deterrent from any attempts to do this. The final stage of the process is when the larval form of the xenomorph known as a chestburster reaches a stage where it will violently and without warning burst out from the hosts chest region, resulting in a gruesome and excruciating death.