These are settings that apply for all songs.
This enables or disables the Tap button on the main screen. Usually this is on, but disabling the Tap prevents you from accidentally Tapping in a new tempo (i.e. you meant to just press play/pause).
This is a sort of screen saver that turns the screen black after a few seconds of inactivity to extend battery life. When you touch the screen, the normal display returns.
If you use the metronome live through a PA, you might not want the buttons to click when you press them.
This adjusts the overall audio volume of the device. Adjustments here are the same as pressing the volume buttons on the side of the device. Usually this is set to maximum with volume adjustments made on a per song basis on the Song Settings page.