Darthmongoose did a good job of explaining! Someone already mentioned the premium program but they’re not accepting novel pitches right now, which is where you keep full rights to your work and do whatever you want with the story. There’s different contract types.
Studio Tapas, aka Tapas Originals, is more exclusive to the site only and are excepting series pitches, but they work with you with your story, suggest changes, help edit, etc. Some novels in this program have become comics.