- 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 your current target is within range of the spell you choose. With no target, or a spell that has no range, it does not match.
Why you might use it
Tells whether your current target is in range of a spell, so a rotation can choose between melee and ranged options: a Classic Hunter switches to Raptor Strike and Mongoose Bite when Raptor Strike is in range, or a Warrior throws or shoots when Mortal Strike is out of range. It is also a quick way to gate a ranged pull ability. See also Beyond Melee Range and Distance.
Example
Raptor Strike is in range
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.