  After a brief introduction into the basic ingredients of electroweak theory
as a spontaneously broken local, non-Abelian gauge symmetry, the general
properties of the electromagnetic current and two-photon operators are
discussed. The specific forms of vector and axial one-nucleon currents are
given, together with lowest order $\pi$ meson exchange and isobar currents as
well as meson production currents. A brief overview is given on the most
important one- and two-boson processes. Electron scattering in the one-boson-
approximation is then considered in greater detail. Formal expressions of the
cross section for inclusive and exclusive processes are given, including parity
violating contributions from $\gamma$-$Z$ interference as well as from parity
violating components in the hadronic wave function. Specific electromagnetic
reactions on the deuteron are then discussed with respect to the influence of
meson exchange currents, isobar configurations in the deuteron groundstate,
relativistic contributions and the role of $\pi$-meson retardation.
Furthermore, recent results on coherent and incoherent $\pi$- and
$\eta$-photoproduction are presented as well as a discussion of the
Gerasimov-Drell-Hearn sum rule and the effect of a parity violating deuteron
component on inclusive electron scattering off the deuteron for quasifree
kinematics. The review closes with a summary and a brief outlook.
