Aspirating is when stuff sent to the stomach goes down your windpipe instead. Choking is when food blocks your windpipe, which can happen as you are aspirating. Gagging and coughing is your bodies attempt to force the stuff UP and out into the esophagus, so if it works you don't actually aspirate. When you swallow your larynx comes over the windpipe, blocking that route to direct food to your stomach via the esophagus. Weak/spastic larynx can cause it to be slow or cover incompletely, letting some food or drink into your windpipe. This doesn't have to cause choking or coughing though. If your larynx/other muscles in the region are TOO weak or unresponsive, you may not feel the aspiration at all: "silent aspiration". Aspiration is bad because your mouth has lots of bacteria that are for digesting food, but hurt your lungs. Each time you aspirate, you put mouth bacteria in there and risk pneumonia. Aspiration pneumonia is why aspiration is serious and should be kept to a minimum.