What is meant by "my food went down the wrong tube"?

When food is swallowed, it travels down the throat, which is the common conduit for food, drink and air. Midway down the neck, the throat branches. The front branch, the trachea, channels air towards the lungs. At the top of this branch is the larynx. Just behind the larynx is esophagus, which is the tube that directs food to the stomach. As a person swallows, the soft palate closes off the nasal passages so that food doesn't get pushed up into the nose. As the throat squeezes food towards the esophagus, the larynx tips forward to allow the food to pass through, and the epiglottis seals off the airway to prevent food from going down into the trachea. Eating while talking or laughing can sometimes cause the larynx to be slow in sealing off the trachea, allowing a bit of food or drink to head towards the lungs. This triggers a strong coughing reflex to prevent aspiration.