A collective slang term generally used to describe a character who relies primarily on spells rather than weapons, although it can be used to refer to any profession capable of casting spells. All current caster professions have 4 energy regeneration.
These are the professions that the term caster is generally used to refer to. Elementalists, Mesmers, Monks, Necromancers & Ritualists fall into this category. The vast majority of these professions' skills are spells, and they have few if any attack skills. All pure casters get +2 energy regeneration, +10 maximum energy and a maximum AL of 60 on their basic armor, and have wands, staves and foci tied to their attributes.
These are professions that are capable of casting spells, but are less focused on them. The two caster hybrids are Assassins and Dervishes, both of which are caster / melee hybrids. Both professions have +4 energy regeneration, +5 energy and a maximum AL of 70 on their basic armor. Both caster / melee hybrid professions have a single weapon mastery attribute tied to a two-handed weapon, with no weapons or off-hand items tied to any other attributes.