On March 19, 2011, the moon was full when it passed within 231,000 miles of Earth, the closet pass in almost 20 years -- the moon's perigee -- the closet point in its eliptical orbit around Earth. A true "super moon" (as this was) is a new or full moon which occurs with the moon at or near (within 90% of) its closest approach to Earth in a given orbit (see http://www.astropro.com/features/articles/supermoon/)