The Second Planck Catalogue of Compact Sources is a catalogue of sources
detected in single-frequency maps from the full duration of the Planck mission
and supersedes previous versions of the Planck compact source catalogues. It
consists of compact sources, both Galactic and extragalactic, detected over the
entire sky. Compact sources detected in the lower frequency channels are
assigned to the PCCS2, while at higher frequencies they are assigned to one of
two sub-catalogues, the PCCS2 or PCCS2E, depending on their location on the
sky. The first of these catalogues covers most of the sky and allows the user
to produce subsamples at higher reliabilities than the target 80% integral
reliability of the catalogue. The PCCS2E contains sources detected in sky
regions where the diffuse emission makes it difficult to quantify the
reliability of the detections. Both the PCCS2 and PCCS2E include polarization
measurements, in the form of polarized flux densities, or upper limits, and
orientation angles for all seven polarization-sensitive Planck channels. The
improved data-processing of the full-mission maps and their reduced noise
levels allow us to increase the number of objects in the catalogue, improving
its completeness for the target 80 % reliability as compared with the previous
versions, the PCCS and ERCSC catalogues.