- 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 you know the spell you choose, or your pet does when Pet spell is ticked. It does not check cooldown, resources, range or whether the spell can be cast right now.
Why you might use it
Checks whether you, or your pet, know an exact spell ID. One rotation can then grow with your character: include Bloodthirst only once it is talented, or use a Hunter pet's Growl only if the pet has learned it. An unlearned spell simply makes the condition false; it does not check cooldown, resources or range. If the game cannot say whether a spell is learned, the condition is unavailable even under NOT. See also Spell Available and Talent.
Example
You know Bloodthirst
Settings
What each setting in the condition editor means, from the game's own help.
Check whether you or your pet know this exact spell ID. An unlearned spell is a valid condition that returns false, so the same rotation can adapt as you learn abilities. This does not check cooldown, resources, range, or whether the spell can currently be cast. Missing or restricted learned-state data stays unavailable under NOT.