- 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 you currently have a pet out. It does not check whether the pet is alive, in range or able to act.
Why you might use it
Check that you have a pet out. Hunters, Warlocks and Unholy Death Knights can put Call Pet, a demon summon or Raise Dead at the top of the rotation when no pet exists, gate pet commands behind having one, or use it as a switch condition between a pet and a petless rotation. It does not check that the pet is alive, in range or able to act. See also Have Named Pet and Pet Spell Available.
Example
you have a pet
Settings
What each setting in the condition editor means, from the game's own help.
Matches when your pet unit exists. This does not check whether the pet is alive, in range or able to use an ability.