system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: what does it mean to “sing from the diaphragm”? And is there a physical sensation that tells you you’re doing it properly?
gpt
When you breathe, you expand your lungs either by moving your shoulders up and chest out, or by expanding downward into your abdomen which allows for a bigger breath. When you breathe and your belly expands, that’s breathing with your diaphragm. The diaphragm is a sheet of muscle just under your lungs at the top of your belly which pulls open the lung cavity helping it expand fully and then can be used to push the air out in a controlled manner. As you sing, your belly should slowly go back in as the diaphragm pushes the air through your voice box. Then breathe in again through a relaxed mouth and throat and your belly should expand out again (no shoulder movement) That’s how you know! 

If you are still having trouble, try laying on the ground  flat on your back with a hand on your belly and then take a deep breath. Watch your belly and hand rise. Pay attention to how that felt and see if you can do it standing up. 

Happy singing!