It's using sparse voxel octree for storing the data, and surface nets for meshing the isosurface into a mesh.
This approach opens a lot of possibilities, for creating complex, organically-looking 3d shapes. The library can be easily combined with particle simulations, agent-based drawings, or for example sampling data from images (technique explored by Karsten Schmidt back in 2018).
For more information and examples go to github: szymonkaliski/volume-brush.