I often encounter terms such as (Helmholtz, Gibbs) free energy, potential energy and total energy when describing the energy of a physical system at atomic level. Sometimes I stumble upon Coulomb energy, which adds more to the confusion. My (vague) understanding is that potential energy of a cell should be equal to Coulomb energy of that cell.
Could someone explain the differences/similarities between these terms, including what contributes to the "total energy" found in a DFT (VASP) calculation?