The description isn't that obvious for people that don't know what notational velocity is or how it works.
It is just a note-taking app for Mac.(https://en.wikipedia.org/wiki/Notational_Velocity)
NV has become popular because of its speed. Your notes are instantly searchable in the top bar of NV. You just type in what you're looking for, and the list of note files -- and they're all just text files -- limits itself to files that contain your search string, and it happens basically as fast as you can type.
It's pretty great. I used it heavily until I started using OrgMode a couple years ago, but missed it enough that I sought out an emacs mode (Deft) that is a workalike.
And the gif, which I usually like, suffers the same problem. Hard to follow unless you already know what it is.
In the end I decided it wasn't for me, tons of small files, each per note? Didn't seem that compelling to me, I think I would prefer one or a few larger files maybe something like vim-wiki.
But because I couldn't quickly research it feel I might have misunderstood it.