Zombies are an undead rotting corpse that is alive yet dead and have voracious appetites for living flesh.
The creation of a zombie varies depending on the story. The cause can be through mystical means, such as magic, voodoo, or other monsters; or even through scientific means. Often used as minions or an army. Some Zombies have control of them selves and have no desire to eat flesh.
The Zombie concept has appeared in many manga and anime series.
In the Highschool of The Dead franchise the zombies fall into the more cliche sort of mob army that is seen in most. Being bitten and dying by one of these creatures will soon count you among their ranks. In the story, a group of students and a teacher band together to survive try to survive the zombie apocalypse.
Ayumu, the protagonist of the story is a zombie. When he is killed by a serial killer, he is revived by necromancer Eucliwood Hellsythe. He is pretty much the same as he was before, he can still eat normal food but he is easily dried out by the sun. He also doesn't die from fatal injuries.
In the manga/anime series One Piece, by Eiichiro Oda. The zombie concept was used during the Thriller Bark story arc. Though, the manner of how they were created was rather unique. The Shichibukai, Gecko Moria, had an island that also served as his pirate ship called Thriller Bark. He commissioned Dr. Hogback to assist him in creating a special zombie army for him. Since he had lost his human pirate army in the New World, the second half of the Grand Line.
Moria had ate the Devil Fruit the Kage-Kage Fruit that gave him control over shadows. With this power he could steal the shadows of living people and transfer them into the reconstructed dead bodies made by Dr. Hogback. The body would retain much of the personality of the shadow's owner, but as it became more acclimated to the new body. The zombie's loyalties would strengthen to Moria and all of those under his command. Unlike most zombies, being bitten can not make one into a zombie.
These zombies were incredible strong. Oddly enough, they were incredibly fast runners. Though only at short distances. They have next to no stamina. It doesn't take long to the point where they are so exhausted that they can't even walk.
The zombie's weaknesses include the classic one of fire. They also have a weakness to salt. If enough salt was to be placed in the zombie's mouth. The bond with the stolen shadow would weaken and it would return to the shadow's original owner.