When a beverage is "going down the wrong pipe", what exactly is happening?

You might have aspirated a bit down your trachea (windpipe) rather than your esophagus. Or, maybe the liquid has irritated your esophagus. But I’m not a doctor, just a person who seems to do this a lot!

You’re trying to cough it out of your trachea and lungs.

@picante has it right, I believe. The “wrong pipe” is your trachea. Food and water is supposed to go down your esophagus to your stomach. Air is supposed to go into your trachea to your lungs. If you aspirate, essentially “breath” in a little liquid into your trachea it doesn’t like it, it only likes air, so you start coughing the liquid out so it doesn’t go into your lungs.

All I know is that I’m having a panic attack, that’s for sure.

If you see here…
The thing called the “Epiglottis” is a peice of thin flesh that closes over your windpipe when swallowing. Sometimes though, due to a unusual postion, or the speed of swallowing, the epiglottis doesn’t manage to close in time and that means the food/drink is able to get into the trachea ( Windpipe ).

Your body is trying to ensure that you keep on breathing.

Theres 2 “pipes” right? A pipe used to swallow and one to breathe.
It’s simply when what your swollowing goes down your breathing tube making to hard to breathe and causing you to cough, pushing air on what you swallowed.

It’s one of those stupid evolutionary quirks that have the feeding pipe and the breathing pipe in the same place.

@MilkyWay is completely correct!