What Does the Auto Attack Button do?

[Akuha]

Not relevant for starting your attack at all on gamepad. Hit A/cross while targeting any enemy to start auto-attacking them.

The purpose of the command is to stop auto-attacking without losing your target, if, for some reason, you want/need to do so.

I don't even use the button, it's a waste of a hotbar slot. If I need to stop attacking something I just take the extra small fraction of a second to hit square then x (Submenu -> Stay Attack).