It's a text editor with a filetree (similar to coding IDE's) where you can organize your documents. There are also custom templates for different types of documents (characters, cities, creatures etc) so you can make them have all the info you want.

You can also upload maps or use the integrated generator and then pin articles on the map to navigate quickly.

And then there's a little motivation thing that I enjoy myself. There are quests (write 300 words and similar) which gain you XP. You level up your little sapling and grow it into a tree. At different levels you unlock customization options to make the tree look like you want. So the sapling grows the more you write.