- 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 off cooldown, counting a cooldown that ends with the current global cooldown as ready. It does not check range, resources or whether you know the spell.
Why you might use it
Tells whether a spell is off cooldown, or will be by the end of the current global cooldown. It is typically used to look at a different spell than the one being suggested: use Slam only when Mortal Strike is not available, or show a cooldown reminder for Recklessness or Avenging Wrath when it is ready. It checks the cooldown only, not whether you know the spell, have the resources or are in range. On Retail and WoW Forever it uses flags the game always shares, so it keeps working in combat. See also Spell Cooldown and Spell Known.
Example
Mortal Strike 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.