This scene is based on the component MeshTetraStuffing to generate from a surface mesh a tetrahedral mesh. Note that this can also be done using the CGAL plugin (which you would need to compile).
This scene is not a simulation, it only generates a volumetric mesh from a surfacic mesh. Unlike surfacic meshes, volumetric meshes represent the interior volume of an object. The goal is to create this mesh and export it as a VTK file to use it later in another simulation.
The MeshTetraStuffing component needs some crucial parameters to generate good quality meshes.