  We show that the pure spinor formalism proposed by Berkovits to covariantly
quantize superstrings is a gauge fixed, twisted version of the complexified n=2
superembedding formulation of the superstring. This provides the Berkovits
approach with a geometrical superdiffeomorphism invariant ground. As a
consequence, the absence of the worldsheet (super)diffeomorphism ghosts in the
pure spinor quantization prescription and the nature of the Berkovits BRST
charge and antighost are clarified. Since superembedding is classically
equivalent to the Green-Schwarz formulation, we thus also relate the latter to
the pure spinor construction.
