What do air bubbles in the toilet mean?

I assume that you mean bubbles in the toilet bowl. I would think that there is a stop up in the drain line somewhere bellow the commode and that another plumbing fixture or appliance is running water into that line and since the air that is traped in that line is being replaced with water the air has to go somewhere.
To unstop this line you will have to snake it, and the best place to do it from, may be the roof

what do air bubbles in the toilet mean?

Air bubbles occur when a partial blockage produces a backflow consisting of a bubble of sewer gas. This can be addressed in one of two ways.
1) you can pull the toilet and snake from there, **or**
2) you can snake from the lavatory roof vent.
If you go down the roof vent put out enough snake to reach the base and 18 feet more. Good luck, n Tom

I had air bubbles in my toilet when my washing macine empties. My plumber changed the studor vent located under the bathroom sink and that solved the problem.

I had air bubbles in my toilet when my washing macine empties. My plumber changed the studor vent located under the bathroom sink and that solved the problem.
Thanks for the update. That faulty AAV was the same as a clogged bathroom roof vent. Tom