Imbue refers to a temporary enhancement that can be added to equipment. Any piece of equipment can only be the subject of a single imbue at a time. Subsequent attempts to imbues will overwrite any existing imbue, but not before asking if you want to do so. Imbue effects stack with existing permanent enchantment effects. Imbues provide a variety of effects and can greatly improve gameplay.
For list of all permanent enchantments see Enchantments by slot.