A Supermoon is when the full moon or new moon is closest during its elliptical orbit around the Earth. The more scientific term is perigee-syzygy of the Earth-Moon-Sun System.
The next occurrence will be on 23 June 2013. This full moon will not only be the closest and largest full moon of the year, it also presents the moon’s closest encounter with Earth for all of 2013. The moon will not be so close again until August, 2014. Check out Supermoon on Wikipedia
Get out your cameras and telescopes and watch the show.