There is much debate on what defines a being to be a zombie. Actually zombies can be broken down into different categories. I'll BRIEFLY describe some of the well known types, not ALL of them. Feel free to add information or tell me how far off I am you ass!
For example, the zombies you battle in the Resident Evil series(1 through 5 with many other suck dick side games) are humans turned into biological montrosities by being injected or coming into contact with different strains of virus's or other zombies that contracted the virus. Later in Resident Evil 4 and 5 the zombies are different than the first 3 games. People turn into zombies in the 4th and 5th installments by being forced fed a type of living organism or again, being injected with the virus. Dead bodies and animals can be reanimated much like the original zombie movies. In some cases the zombies will weild machine guns, stun rods, rocket launchers and shotguns. All of the zombies in the game series DO NOT thrist for brains or blood. They do not need any nourishment from a living body. They tend to blow your ass up or maul you to death. These zombies DO NOT turn you into a zombie. They are fast and agile and have the basic motor skills of humans. Some of these undead have special abilities and some can turn into huge monsterous creatures that have qualities of different animals or humans. Example, you fight a giant vampire bat with the legs and the tail of an insect or scorpion in Resident Evil 5. These zombies do share some qualities of the original but not all. Honestly, I would rather call these zombies "infected organisms" due to the fact the virus's or the "Las Plagus" alter and transform some of the hosts. Decapitation, grenades, unconventional weapons, and mutliple shots from conventional weapons are the best ways to drop these type of zombies in of all the games.
Voodoo zombies are more than likely the real origin of zombie lore. Some say dead people were brought back from the grave to run amuck in society creating chaos and murder. Some were brought back for the shamans biding. Others believe they were brought back from the grave to complete unfinished business, such as a person wrongfully murdered. When bitten by these zombies you do turn into a zombie. They did feed for nourishment or were used as a weapon and then decapitated after their "job" was fulfilled.
The Night of the Living Dead type zombies are by far the best well known type of zombies in America and quite possibly the world. These zombies were actually reanimated to the land of the living much like their voodoo cousins but they do differ from them also. These zombies were lethal in numbers even though they were slow enough for an average person to run away from in an open area. They trapped and killed their victims by sheer numbers. For some odd reason the humans in these films tried to hold up in houses only to have their barricaded walls and doors knocked down by hundreds of the slow, lumbering zombies. They do feed on humans for nourishment. Decapitation seemed to be the only way to stop them.
Like I said in the beginning there is much debate on what makes a zombie a zombie. Do they have to move fast or slow? Do they kill humans out of rage much like the 28 Day Later film or kill for nourishment? Are they the undead or Lucifers overflow of bodies coming from hell?
One thing is for certain. Zombies and their undead counterparts are a pop culture phenomenon, have been always will be. Clothing, bands, comic books, magazines, movies, cartoons, games any form of media has been infiltrated by the "zombie horde". Some people around the globe actually have started organizations to prepare for the undead awakening. There is also a very popular book simply named "The Zombie Handbook" that will inform a person on detailed information on zombies, where to hold up, what not to use against zombies, so on and so forth.
Aim for the head and yes, zombies can climb. Oh yea and some have supernatural strength! ;)
Damn Joe thanks for watching my back! Now zombies
are eating my brains from my skull like ice cream!
Zombies Ate My Neighbors!
28 Days Later
I Am Legend
Return of the Living Dead
The Night of the Voodoo Zombie Nigga