We have 3 toilets in the house and anytime one of them is flushed one of the other ones burps/bubbles a lot (enough to splash water out of the toilet). What could be wrong with them? It does not happen when we do laundry or use the shower or dishwasher or sinks.

Most likely have a blockage in the vent that serves these devices. The other ones work since they also have another vent

I agree with ma0641 that you have a blockage. However I don't think it's the vent that's blocked. Let me explain.
Gurgles are caused by suction caused by a blocked vent while bubbles are caused by back pressure which is caused by a blockage in the drainage line.
You have a blockage downstream from the toilet that's doing the bubbling.
The solution would be to:
1. Pull the toilet and snake the line from there **OR**
2. Snake from the lavatory roof vent. Good luck, Tom

Next time I'm listening for gurgles and bubbles, I'll remember that! Brian