It's a visual programming environment for .net (the current stable version is based on .net6 while newer previews use .net8). Visual in the sense that
programs are represented as node graphs.[1]
You can basically do what ever you could with C#. Using the VL.Fuse[2] library you can also visually program on the GPU. If stuff is missing you can reference just about any nuget package or add functionality using C# (CPU) [3] or HLSL (GPU)[4].
The way it works seems to appeal to "artists" / "creatives".
It's pretty simple to get a visual output fast and the always running (hot-reload) aspect makes it easy to iterate on things, tweak some parameter (size, speed, color) and directly see the outcome.
normal industry projects
It's used quite a lot in the context of trade fairs, not only for touchscreen exhibits but also stage shows. Nice example: https://nsynk.de/work/mercedes-iaa15
There are also totally different kinds of projects/uses, they are just not that well documented. For example I know of a guy that programmed a feeding robot for a fish farm using vvvv.
I started out at meso (~2005) and I worked for them for quite some time but I am not really one of the meso guys. tbh I landed there by chance at the recommendation of a friend while looking for a place to write my diploma thesis. at that time I had no idea whatsoever what they were doing and no relation at all to "digital arts" or "generative design".
Check https://visualprogramming.net instead. There are two versions of vvvv the old one called "beta" and the newer one (complete rewrite) called "gamma". vvvv.org is more focused on the old version.