Downgrading apps: Allows you to downgrade your apps. You can install older app version over newer one without app data loss.
Installing unknown apps: Allows you to install apps from unknown sources. You can sideload any app.
Installing apps on external storage: Allows you to install all apps on the external SD card. Experimental feature (may or may not work on some device, can cause bugs), requires enabled Expert mode.
Auto installing: Allows you to automatically start installations, so you don't have to click on Install button to start installations.
Auto closing after installing: Allows you to automatically close installations, so you don't have to click on Done button to close installations.
Auto hiding when installing: Allows you to automatically hide installations, so you don't see any user interface related to installing.
Auto launching after installing: Allows you to automatically launch app after installations, so you don't have to click on Lauch button to launch app.