World Anchor Features

Always active unless out of fuel or disabled with Redstone.
Force loads chunks on world load.
Personal Anchor Features

Only active if the owner is currently logged into the Game.
Does not force load chunks, only prevents already loaded chunks from unloading.
Admin Anchor Features

Don't need Fuel.
Always active unless disabled with Redstone.
Force loads chunks on world load.
Passive Anchor Features

Similar to Personal Anchor it does not force load chunks, but keeps them loaded once they have been visited.