Use Default Splashscreen: This makes the blue retropie splashscreen the default splash screen (the splashscreen you see the first time it boots up).Disable Custom Splashscreen On Boot: Select this option to disable splashscreens on boot.Enable Custom Splashscreen On Boot: This is pretty self explanatory- if you've disabled splashscreens the you select this to re-enable splashscreens on boot.
( Note you may need to install or restart samba shares from the setup script for the splashscreens folder to show up over samba shares) Make sure you create a new folder to place your splashscreen in- for example: /home/pi/RetroPie/splashscreens/video/yourvideo.mp4 Choose Own Splashscreen: Once you've opened up the splashscreen menu in the setup script at least once a folder will be created in /home/pi/RetroPie/splashscreens you can also access this splashscreens folder from samba shares once its created.