A super moon is the coincidence of a full moon or a new moon with the closest approach the Moon makes to the Earth on its elliptical orbit, resulting in the largest apparent size of the lunar disk as seen from Earth. The technical name is the ‘perigee-syzygy’ of the Earth–Moon–Sun system. The term super moon doesn’t come from astronomy. It comes from astrology, and the definition is pretty generous so that there are about 6 super moons each year.
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 lead to formation of super moon. There are 4-6 Super moons a year on average.
The new moon or full moon has to come within 361,524 kilometers (224,641 miles) of our planet, as measured from the centers of the moon and Earth, in order to be considered a super moon.
All full moons (and new moons) combine with the sun to create larger-than-usual tides, but closer-than-average full moons (or closer-than-average new moons) elevate the tides even more. Spring tides accompany the super moons.