Airline lavatories are usually pretty simple. To be sure some passengers fail to use them, sometimes they’re inoperative and sometimes other passengers stink them up, but for the most part they work the same way. The only thing that confuses passengers is which one are they allowed to use?
This long-controversial question has been settled on United Airlines: to reduce bunching of passengers waiting in line for the loo, they may now use any lavatory on the plane. This is a coronavirus distancing measure.