A supermoon is a full moon that occurs when the moon is closest to the Earth in its elliptical orbit. The effect is to make it look larger than normal. The technical name for this is perigee.
The supermoon on Dec 3, 2017 is shown here with a plane as it takes off from Ronald Reagan National Airport in Washington, D.C. and in the area of the Capitol building.
Two more supermoons will occur next year on January 1 and January 31.