- Not available on that edition (the reason is in the tooltip)
- Depends on the setting, your class or another addon (details in the tooltip)
What it does
Checks whether the slot you choose (main hand, off hand or ranged) holds the kind of item you choose, such as nothing, any weapon, a two-handed weapon, a shield or a specific weapon type like Daggers.
Why you might use it
Checks what is in your main-hand, off-hand or ranged slot: nothing, any weapon, a one-handed, two-handed or ranged weapon, a shield, an off-hand item, or a weapon type such as Daggers. It works well as a switch condition: a Rogue uses Backstab only with a dagger in the main hand, a Warrior plays Shield Slam only with a shield, and a dual-wield build checks the off hand for a weapon. The ranged slot exists only before Mists of Pandaria, so it is unavailable on Classic progression (Mists) and Retail, and also while item data is loading. See also Have Item Equipped and Weapon Swing Time.
Example
your Main Hand slot holds Daggers
Settings
What each setting in the condition editor means, from the game's own help.
What is equipped in the main hand, off hand or ranged slot: nothing, any weapon, a one-handed, two-handed or ranged weapon, a shield, an off-hand item, or one weapon type such as Daggers. Types are read from the item's class and subclass, so they work in every language. The answer is cached until your equipment changes.
Dual wielding: off hand holds any weapon. Titan's Grip: off hand holds a two-handed weapon. Backstab and Ambush: main hand holds Daggers. Shield Slam or a tank set: off hand holds a shield. The ranged slot exists only before Mists of Pandaria; elsewhere, and while item data is still loading, this condition is unavailable, including under NOT.