Hello!
The orbits of the planets around the Sun and the orbit of the Moon around the Earth are not circular. They are actually elliptical, as discovered by the astronomer Joannes Kepler. For the orbit of the Moon (or a man-made satellite) around the Earth, the closest point along the orbit to the Earth is called perigee, and the furthest point away from the Earth along the orbit is called apogee. The full moon on Saturday occurred less than one hour away from the perigee of the Moon's orbit around the Earth. This happens about every 18 years, so the next time should be in 2029. However, you can view the Moon near perigee in other phases.
See these links for more information.
http://science.nasa.gov/s...011/16mar_supermoon/
http://fourmilab.ch/earthview/pacalc.html
Kris