- 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 if the spell you choose is ready to cast, for any spell rather than only your specialization's own. A spell waiting only on the global cooldown counts as ready.
Why you might use it
Checks whether a spell is ready to cast right now, for any spell ID rather than only the spells your current specialization's spell picker offers. Reach for it when the spell you care about is not one of your spec's own abilities, such as a racial like Berserking, an ability granted by an item or zone, or a spell from another spec; for your own class abilities, Spell Available is the usual choice. A common use is a cooldown reminder that lights up a racial whenever it is ready.
Example
Berserking is available
Settings
What each setting in the condition editor means, from the game's own help.
The icon next to the spell name will automatically update to display the spell that is currently selected. You can drag a new spell from your spell book or action bars into this icon slot to replace your selected spell.
Use this exact spell rank - Unticked (the default), any rank of the spell matches. Ticked, only the rank you chose matches. (only on Classic Era, TBC Anniversary, Forever)
Spell - This is a specific spell used in this condition. You may drag this spell from your spell book or action bars into the input field or spell icon to set this value. This input field has prediction enabled, so you do not have to type the full spell name, just select from the prediction frame when it appears.