Played with it a little. Found out a Mesh is the surface of a solid. Like the STL file. So not too much use for FEM.
Mesh could exports to a Nastran nas/dbf file. that's cool.
When you import a 3D STL, the model could be shown up. But if import a 2d Nastran mesh, nothing show up. Could STL save a 2d plane mesh?