  We consider general aspects of N=2 gauge theories in three dimensions,
including their multiplet structure, anomalies and non-renormalization
theorems. For U(1) gauge theories, we discuss the quantum corrections to the
moduli space, and their relation to ``mirror symmetries'' of 3d N=4 theories.
Mirror symmetry is given an interpretation in terms of vortices. For SU(N_c)
gauge groups with N_f fundamental flavors, we show that, depending on the
number of flavors, there are quantum moduli spaces of vacua with various
phenomena near the origin.
