Default Journal
For comparison, this is the default pet journal without any addons:
Pet List
This is the searchable list of pets. When entering text in the search box it will look for pets with the entered text in the pet's name or its source.
Loaded Pets
These are the three battle pet slots. You drag pets from the pet list to here to choose which will fight. Each pet can choose three abilities. Pets and abilities cannot be changed while in battle.
Pet Information
This area displays some information about the selected pet, including its stats and possible abilities. Mouseover of the pet's icon in game will display information about where it's from.
Total Pets
The total pets is the number of pets you own, including duplicates.
Revive Battle Pets
This button will heal all injured pets. It has a 4 minute cooldown and is automatically put on cooldown when you log in to prevent swapping to alts to heal.
Summon Button
The Summon button will summon a selected pet or dismiss one if it's already out. Pets are also automatically summoned when slotted in the first battle pet slot. For many this is an undesired feature but there's nothing addons can do to stop it.
Find Battle Button
The Find Battle button will queue you for a matched battle with another player in your region. When another player is found you'll get a confirmation popup that takes you into battle.