A super moon happens when a full moon is at it's closest distance to the earth. super moons appear up to 14% bigger and 30% brighter.
During a super moon tides vary up to 2 inches more than regular tides but there is no evidence of a link between super moons and natural disasters.
In the diagram below, Apogee and perigee refer to the distance from the Earth to the moon. Apogee is the farthest point from the earth. Perigee is the closest point to the earth and it is in this stage that the moon appears larger.