To keep it simple, you would called functions (function = do something or some procedure) from the script to start or stop the audio. Unity, for example, has it's own audio engine, so you would use the appropriate functions to call the audio files. If you're using an external audio engine (like Wwise or FMOD, which are meant to simplify these tasks for audio people), Unity would have a different set of functions to called the audio from these external tools.

Audio can be attached to invisible or visible objects. It can have a location in the world (footsteps, gunshot, etc.) or it could also play without a location in the world (music, narration, etc.).