- 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 cast the spell you choose at a point in your recent casts that matches the count you set, where 1 is your last cast and 2 the one before. Casts older than the Spell History Memory setting are forgotten, and a spell not in your history does not match.
Why you might use it
Looks back through your recent casts by count: 1 is your last cast, 2 the one before. A Windwalker Monk uses it with NOT to avoid repeating the same ability twice in a row for Combo Strikes, and other specs use it to alternate fillers or follow a fixed sequence. Casts older than the Spell History Memory setting are forgotten. On Retail and WoW Forever a cast the game hides is recorded as unknown, which makes the check unavailable at that position. See also Spell Cast History Time.
Example
Tiger Palm was cast exactly 1 casts ago
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.
Operator - How to compare Spell Cast History with the Count value. This comparison uses basic mathematical comparison operations.
Count - How far back in your spell history to look for a casting of Spell (by count). A value of 1 means your last spell cast, 2 means two spells ago, etc. Each instance of the same spell cast is treated separately. Any spell cast more than the setting of Spell History Memory (seconds) in the primary Rotation Master configuration screen ago will not be available.