- 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 how many seconds are left before your next rune of the type you choose is ready, compared with the number of seconds you set. It uses whichever rune of that type comes back soonest, and a ready rune counts as zero.
Why you might use it
For Death Knights on Classic progression (Mists), compares the seconds until the next rune of a type becomes ready. It lets you wait a moment for a rune instead of using a weaker filler, for example holding Heart Strike when a Blood rune is less than a second away, or using Horn of Winter only when no rune is about to come back. It does not exist on Classic Era, TBC Anniversary, Retail or WoW Forever. See also Runes.
Example
the cooldown on your next Blood rune is less than 1 seconds
Settings
What each setting in the condition editor means, from the game's own help.
Rune Type - Which type of runes you wish to check.
Blood
Unholy
Frost
Death
Operator - How to compare Rune Cooldown with the Seconds value. This comparison uses basic mathematical comparison operations.
Seconds - The number of seconds until a Rune Type rune becomes available.