- 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 much mana the unit specified has, compared with the number you set. A negative number compares how much mana the unit is missing from its maximum instead.
Why you might use it
Compare a unit's mana as a raw number; a negative value compares missing mana instead. Raw values suit fixed costs, such as keeping enough mana for an emergency heal by blocking expensive spells below a set amount, or using a mana potion only once you are missing at least what it restores. Not available on Retail or Forever, where the game hides mana values from addons. See also Mana Percentage.
Example
your mana is less than 1000
Settings
What each setting in the condition editor means, from the game's own help.
Unit - The unit this condition uses as the target of comparison.
Operator - How to compare Mana with the Mana value. This comparison uses basic mathematical comparison operations.
Mana - The raw mana value of Unit. If this number is negative, it means the mana deficit (from max mana).