This app can display the data produced and managed by Song Database if the file is accessible via URL (web address). It cannot be used for anything else, so if you don't use Song Database, this app isn't meant for you!
You can view the song lyrics, any available translation and the guitar chords (if available). Translation and chords can be disabled in the settings. The app keeps a local version of the data until it can fetch an update (after a timeout which is three days by default) so you can use it offline as well.
If you are the administrator of your Song Database installation and don't want to upload the file containing the songs every time you modify it, you could set up a synchronisation solution like Nextcloud and use the "share link" functionality - the resulting link has to be used in the app.