- 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 health the unit specified has, compared with the number you set. A negative number compares how much health the unit is missing from its maximum instead.
Why you might use it
Compare a unit's health as a raw number; a negative value compares missing health instead. Raw values suit fixed thresholds, such as using a Healthstone once you are missing more than it restores, or holding a long cooldown for targets with plenty of health left so it is not wasted on trash. Most rotations are better served by Health Percentage, which scales with level and gear. Not available on Retail or Forever, where the game hides health values from addons.
Example
your target's health is greater than 50000
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 Health with the Health value. This comparison uses basic mathematical comparison operations.
Health - The raw health value of Unit. If this number is negative, it means the health deficit (from max health).