difference between bubbler and a bong

Me and my buddy were havin our daily sesh and we got to talking about his new peice and i said it was a bubbler and he said it was a bong then we were trying to establish the difference and i just want to know what everone else thinks is the difference. I think it all has to do with how the air comes in to clear the chamber if the air travels through water... bong. Although if the air cromes stright in say though a blast that makes it a bubbler. What do you think