CBSE Class 10 Answered

At the back of your throat, food and air both travel through the same tube for a short distance until the tube divides into two tubes – one is the oesophagus which carries food down into the stomach, and the other is the trachea (windpipe) which carries air to the lungs. There is a small flap at the top of the trachea called the epiglottis and this closes off the top of the trachea when you swallow some food or a drink. 

While talking, there is a chance that food can slip past the flap and into the windpipe – which can block the windpipe. This is called 'choking'. Coughing is an automatic reaction trying to push the lump of food up out of the windpipe. Most of the time we can cough the lump out.