VASP terminology

Exchange-correlation function: LDA: Local density approximation, using explicit analytic function of E_xc GGA: correction to LDA at large magnitude of gradient in the number density.

    - PBE-GGA, PW91-GGA, ..., attempts to use different form of E_xc

Pseudopotential: OPW: separation of core region and valance region. valance region is described by a smooth function Ultrasoft Pseudo potential: even core region is described by a smooth function PAW: correction to ultrasoft pseudopotential by considering the whole wave function to compensate the discrepancy between localized function and ultrasmooth function in the core region