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].

[1]https://en.wikipedia.org/wiki/Node_graph_architecture

[2]https://github.com/TheFuseLab/VL.Fuse

[3]https://thegraybook.vvvv.org/reference/extending/overview.ht...

[4]https://thegraybook.vvvv.org/reference/libraries/3d/shaders....