Minecraft wiki entry for Sound_(disambiguation), associated text: Ambience - Various sounds that can be heard if conditions are met. They are meant to make gameplay more climatic.
Music - Music made by C418 and Lena Raine that plays randomly.
Loops - Unused sounds found in files that loop when in specific places such as underwater.
Sounds.json - A file that tells the sound system what sound files to play when a sound event is triggered.
/playsound, /stopsound - Commands used to play or stop playing any sound event defined in Sounds.json.
The sounds made by mobs, entities, items, blocks and/or players.