People can learn singing by by using cavities in their body differently.  One thing you want to do is learn how to sing from your diaphragm.  If you can view your mid section pushing out, you are using your diaphragm with your breathing.  Then, when you exhale,  your stomach comes back in.  Most people just don’t breathe correctly and this is especially true when they are trying to sing.  If you practice breathing with your diaphragm, you will soon see how beneficial it is to singing because it makes it easier.  It will also help you hold notes a lot longer when you sing out after an inhale.