Press the button to backup your album and playlist data from spotify.
You will be able to download a json file containing all your albums and playlists.
This only backs up your spotify data, it does not backup the actual audio files.
This app can only access your spotify data for an hour. After an hour, all data is deleted and you will no longer be able to download your backup.
If you don't want to trust this app with your spotify data you could also run it yourself, see this github repo.