Zombies are, essentially, living golems. A dead body is healed and reanimated with another spirit. The interesting difference lies in the fact that a zombie's brain has been used before. They retain snippets of memories from their body's previous life, made hazy by death. They also have memories of other lifetimes, and of the world beyond, about as distant as those of other golems.
Sometimes, zombies occur naturally, when a free spirit inhabits a corpse, for whatever reason. In such cases, without magical intervention, the resulting creature does not last long. Any damage that caused the death of the host remains, and the body is still quite dead. If decomposition doesn't cut the zombie's "life" short, it is usually preyed upon by fellow zombies hungry for magic, or starves to death for want of the same.
Artificially created zombies are better off. With modern medical magic, it is possible to heal and restore life to certain corpses. Most brain damage can be repaired, enough to make the corpse a suitable host for a complex spirit, without the need for a crystalline brain replacement. Corpses that were killed by blood loss suffer from an intense craving for what they lost, and are unsuitable for reanimation.
As it stands, all zombies, regardless of origin, require two things to sustain themselves - magic, and meat. Naturally occurring zombies usually fill this need by consuming the newly dead, or by picking off living victims. All mortals, and especially mages and telekan, possess a trace amount of magical energy - actually the presence of their spirit - within their brains. By consuming this, the zombie consumes the energy as well, and is able to exist a little longer.
Artificially created zombies are, or should be, fed an adequate supply of meat and magical energy, or they get "hungry", and become berserk and impossible to control. Zombies are infamous for having a tentative control on their natures, and are seen with more fear than golems, partially because an artificially created zombie can't be told apart from a normal mortal until they snap.
Zombies are animated for any number of reasons, usually as servants to the rich, or as expendable minions. Since they've already died, people don't have as many qualms with killing them again. as with golems, there's the risk that a zomibe's spirit will come back, angry, if mistreated, and so they're given grudging respect, rather like the berth given a caged beast.
Especially prized zombies often have their spirit transferred over to a more permanent, golem shell. This is a reward many owned zombies strive for, as it affords them greater status and less chance of getting hungry or dying.
Zombies, being property, cannot own property or become citizens, unless they can hide their nature for long enough to pull it off.
Like golems, zombies can sense the presence of magical energy, and have empathy with fellow spirits, including normal mortals. They can sense the presence of spirits, and, sometimes, basic emotions. Their abilities in this regard are generally weaker than a golem's.
Zombies might not retain the instincts and personality of their host race.