It's essentially an infinite playlist generator! Given some starter tracks, this tool can be used to make countless new playlists for you to listen to.
First, make a Spotify playlist called play-whatever (must be that exact name). Next, fill it with some of your absolute favorite songs. That's it! You're ready to go.
The songs you put in play-whatever are used to find other songs you might like, and they're put in a new playlist called whatever. After generating the whatever playlist, it'll take you right to it, so you can get to listening. If you get tired of whatever, you can come back here and generate a new playlist.
Diversity is the number of tracks that will be used to seed the resulting playlist. For a more uniform playlist, choose a low diversity. For a highly varied playlist, choose a high diversity.