Using this avoids a mechanical shutter entirely, making the shooting entirely silent. The main advantage though for macro shooting is not having vibration due to a mechanical shutter. This feature is sometimes called "silent shooting".
On the Sony a6600, this is in the second set of photo taking menus (with a camera icon and a "2") and is labeled "Silent Shooting" and you can select on or off.
Tom's Computer Info / tom@mmto.org