The symbol is used to denote a Tessellation of regular -gons, with of them surrounding each Vertex. The Schläfli symbol can be used to describe Platonic Solids, and a generalized version describes Quasiregular Polyhedra and Archimedean Solids.
See also Archimedean Solid, Platonic Solid, Quasiregular Polyhedron, Tessellation