"Every dead body that is not exterminated becomes one of them. It gets up and kills! The people it kills get up and kill!" - George A. Romero's Dawn Of The Dead
Zombies are one of the most popular types of monsters in fiction today and have frequently appeared in many Hollywood films. They are among the most common types of "cannon fodder" in action and horror films.
What are zombies?
Zombies are deceased human beings that have been reanimated into savage, mindless creatures. The means of reanimation varies between mediums - common causes of zombies include viral outbreaks or exposure to radiation - but those who had been reanimated typically have no powers of reason or even any intelligence. They are simply walking corpses which, in most media, are driven to seek out and devour the living. People who are killed by zombies are usually infected by whatever contagion the zombies carry and will become zombies themselves, getting up and seeking out living people to eat.
While zombies are often shown to be cannon fodder in many movies, they are not easy to kill. Injuring zombies does not cause them pain or distress and they will not stop pursuing prey unless their brains are destroyed. Shooting zombies in the head is the most effective way of killing zombies in most films, though decapitation and incineration are also good alternatives. Many films show zombies being killed in more creative and absolutely gruesome ways.
Types of zombies
Not all zombies are alike, though the standard for movie zombies was set by legendary horror director George A. Romero, creator of Night of the Living Dead and all of its sequels. It was in Night that zombies were originally shown to feed on living humans and that they were born from recently deceased people affected by cosmic radiation. Many other filmmakers have borrowed this formula and others still have made their own adjustments to the formula to make the zombies more threatening and/or to better detail their origins.
In Paul W.S. Anderson's live-action film series based on Capcom's survival-horror video game franchise, zombies (referred to simply as "Undead" in the films) are people who have been infected by the T-virus, a biological weapon created by the globe-spanning Umbrella Corporation. The zombies are very similar to Romero's zombies, shambling about mindlessly and driven by insatiable hunger. In the fourth and fifth films, however, the Undead population has mutated over the years that the virus has ravaged the Earth and zombies become capable of running and possess a set of tentacular mandibles that emerge from their mouths. The mandibles are actually a trait borrowed from the Majini, a breed of humanoid enemies from the Resident Evil 5 video game. The Majini in the game are not zombies, however, merely people who are being controlled by mutant parasites called Las Plagas.
Las Plagas parasites have also featured in Resident Evil: Retribution. In the Umbrella Prime facility, The Red Queen commands an army of Undead that have been enhanced by these parasites, making them stronger and more intelligent. These zombies are capable of operating vehicles and firearms.