  SN 1006 (G327.6+14.6) was the brightest supernova (SN) witnessed in human
history. As of one thousand years later, it stands out as an ideal laboratory
to study Type Ia SNe and shocks in supernova remnants (SNRs). The present state
of knowledge about SN 1006 is reviewed in this article. No star consistent with
a surviving companion expected in the traditional single-degenerate scenario
has been found, which favors a double-degenerate scenario for the progenitor of
SN 1006. Both unshocked and shocked SN ejecta have been probed through
absorption lines in ultraviolet spectra of background sources and thermal X-ray
emission, respectively. The absorption studies suggest that the amount of iron
is < 0.16 M_sun, which is significantly less than the range for normal SNe Ia.
On the other hand, analyses of X-ray data reveal the distribution of shocked
ejecta to be highly asymmetric especially for iron. Therefore, most of iron
might have escaped from the ultraviolet background sources. Another important
aspect with SN 1006 is that it was the first SNR in which synchrotron X-ray
emission was detected from shells of the remnant, providing evidence that
electrons are accelerated up to ~100 TeV energies at forward shocks. The
bilateral symmetry of the synchrotron emission (bright in northeastern and
southwestern limbs) is likely due to a polar cap geometry. The broadband
(radio, X-ray, and gamma-ray) spectral energy distribution suggests that the
gamma-ray emission is predominantly leptonic. At the northwestern shock,
evidence for extreme, but less than mass proportional, temperature
non-equilibration has been found by optical, ultraviolet, and X-ray
observations.
