Alter Aeon Online Help

Keywords are:  'vnums virtual numbers'

A 'vnum' is like a part number in a catalog, and is used as a way for
gods to look up and find things in the game.  Vnums are generally only
used when building - for example, when editing a clan mob, you may
see that its mob number (or vnum) is 12345.  This number identifies that
kind of mob, and using the mob's vnum, the game can create one or
many copies of that mob.  Keep in mind that this is just like ordering
parts from a manufacturer - if you have the part number, you can order
as many copies as you want.

The reason that vnums are like part numbers is because objects can be
sacced and mobs can be killed.  When a mob gets killed and needs to
repop, the game can just create a new mob using the mob vnum.