Because healing magic is holy, for a long time the only casters who had access to it were the crazy Clerics and the hostile Druids. This, as one might guess, was a problem, as healing magic is very useful. Get hurt while adventuring? Hope those herbs and bandaids are good enough! However, arcane casters (Wizards and Sorcerers) attempted to fill the open niche: eventually, certain low-level holy spells were replicated by the school of magic most concerned with life and death–the Necromancers. They discovered how to cast basic spells like cure wounds and lesser restoration as necromancy spells. (The downside to this is that they must be cast at higher levels than a Cleric/Druid would need to.) Certain spells still eluded them, such as resurrection and the like.
Necromancy quickly became an incredibly important school of magic, studied widely. Due to their dual role of healer and mortician (for Necromancers still practice their traditional roles as well), even the smallest of villages have at least one local Necromancer (similar to how even the smallest villages in medieval Europe had a priest). Sometimes one local Necromancer will travel between a few closely-spaced rural villages. In larger cities, there will be several Necromancer locations, and they tend to specialize more. Necromancers and Enchanters work together to produce healing potions and similar concoctions.
(Note that other schools of magic are still practiced; this is just to emphasize the larger role and general acceptance Necromancers have in everyday society.)
Necromancers, as any specialized group, have professional jargon for common situations. The most well-known of these (nearly in the common parlance) are the S.C.U.B.A. and Z.C.U.B.A. designations for reanimated corpses. They stand for Skeleton Corpse Under Basic Animation, and Zombie Corpse Under Basic Animation respectively. Necromancers will typically append the appropriate designation onto the name of the relevant entity; for example, if a man named Steve is killed and returned in skeleton form, he would typically be referred to as S.C.U.B.A. Steve.
Necromancers often divide themselves into Type S and Type Z, depending on which form of reanimation they prefer, though many also don’t hold a strong preference.