A heartburn is something that you feel if there is a problem in your digestive system. Typically what happens is that you eat something that doesn’t agree with your stomach, and for some reason your stomach acid travels upwards.
It is extremely acidic because it needs to be able to break down foods that you eat, so the different chemical environment in your stomach helps with that. However, it also means that stomach acid is not suitable to be in any other place in your body except your stomach.
If it travels to your esophagus, the tube that connects your stomach and your mouth, you will feel a burning feeling. It typically occurs in your lower chest, right above where your stomach should be. It feels a bit different for everyone, and the duration of the hurt is different as well.
If you have never had heartburn, consider yourself lucky! You can find the approximate location where the heartburn would be by looking for the base of your rib cage, in the center of your body. Right around that area or slightly lower is where your esophagus meets your stomach, and where you would feel heartburn if you have it.
If you have frequent heartburn, you should probably consult a doctor. In some places, you may be able to get over the counter medication to relieve some symptoms, but the root cause is likely related to your diet.