It’s like a spreadsheet, immediately familiar, but much more suitable for complex data because it’s hierarchical.
It’s like a mind mapper, but more organized and compact.
It’s like an outliner, but in more than one dimension.
It’s like a text editor, but with structure.
Have a quick look at what the application looks like on the screenshots page, see how easy it is to use in the tutorial (out of date, the live in-app tutorial works much better!), then give it a download (above).