Some stores, like iTunes or Bandcamp allow you to include other things in your release, aside from the music. This could be some samples, shorter edits, an acapella, or it could be something like a video, a PDF of exclusive information or an interview. The limit with this stuff is really only your imagination (and file-size limits on each platform!).
[I put together a big list of possible bonus content ideas you might like to add to your releases in my premium course *How To Start Your Own Record Label*]