  We present a description of the Australian Dark Energy Survey (OzDES) and
summarise the results from its six years of operations. Using the 2dF fibre
positioner and AAOmega spectrograph on the 3.9-metre Anglo-Australian
Telescope, OzDES has monitored 771 AGN, classified hundreds of supernovae, and
obtained redshifts for thousands of galaxies that hosted a transient within the
10 deep fields of the Dark Energy Survey. We also present the second OzDES data
release, containing the redshifts of almost 30,000 sources, some as faint as
$r_{\mathrm AB}=24$ mag, and 375,000 individual spectra. These data, in
combination with the time-series photometry from the Dark Energy Survey, will
be used to measure the expansion history of the Universe out to $z\sim1.2$ and
the masses of hundreds of black holes out to $z\sim4$. OzDES is a template for
future surveys that combine simultaneous monitoring of targets with wide-field
imaging cameras and wide-field multi-object spectrographs.
