Your heartbeat 😂😂
In your chest it is your heart and lungs. They listen for a strong rhythmic beat from your heart. For you lungs they want to hear air passing through smoothly. If they go lower than your chest they are listening to your GI tract. It should make certain sounds to show it is working, but you don't want too many or too loud of those sounds.
Usually your heart and lungs. Mainly they listen to your lungs from the back but I've had it both ways.