The Back Button Focusing (BBF) technique can allow you to use your camera more efficiently, by giving you greater control over the focus operation and being able to switch between focus modes more easily.
Back button focus is a mode available on many cameras that allows you to separate the focus and shutter operations to different controls, which normally by default are both controlled by the shutter release button - half press to focus and full press to release the shutter.
But by configuring your camera differently, the shutter release button can be set to only release the shutter, and a different button used to acquire focus, normally one on the back of the camera - hence the name back button focus.
But BBF provides a number of advantages over single button focus/shutter operation, explained below.
Easily swap between continuous focus and single focus
Easily lock focus
Avoid focus problems
Easily switch between auto and manual focus
See my Z9 Settings post for details of how to set BBF on the Nikon Z9 camera