For questions relating to the electronic structure of inorganic complexes, particularly the splitting of degenerate $d$ or $f$ orbitals by the symmetry of the surrounding ligands.
Crystal field theory relates the splitting of degenerate $d$ or $f$ orbitals based on the electrostatic field of surrounding ligands. It describes some magnetic properties, colors, but not bonding, which requires a more complete molecular orbital or ligand field theory treatment.