  An intrinsic construction of the tensor category of finite dimensional
representations of the Langlands dual group of G in terms of a tensor category
of perverse sheaves on the loop group, LG, is given. The construction is
applied to the study of the topology of the affine Grassmannian of G and to
establishing a Langlands type correspondence for "automorphic" sheaves on the
moduli space of G-bundles.
