The pain is caused by acid leaking out from your stomach into your oesophagus. This causes the pain we are all familiar with.
It happens to most people from time to time but for some it becomes a regular and unwanted part of life.
There are many simple things you can do to treat it from a slight change in diet to antacids. Read more about the symptoms and treatment of acid reflux here.
Or watch this video from the Mayo clinic
In summary - you can overcome acid reflux and do not have to put up with it.