Bukkit

The promote command is used to quickly increase a player's rank.

Syntax: /promote [player] (choice) (world)

An example would be two different permission trees, 'staff', and 'paid.'

default
  |-----------|
moderator   donor
  |
admin

If you tried to /promote someone who was a default, the system would ask you what rank you wanted to promote it to. The proper usage in the case you wanted the player to be staff would be "/promote someone moderator."

If you wanted to promote that person again to admin rank, a simple "/promote someone" would do, since the permissions don't fork at that location.