perigee

The Moon's orbit around Earth is elliptical which means there are times when it is further away - apogee - and times when it is closer - perigee.

Full supermoons occur when the orbit of the moon is at perigee - the closest point to Earth in its orbit, which makes the Moon appear bigger and brighter in the night sky.

A supermoon occurs when the full Moon coincides with when the moon is at its closest point to earth in its orbit - the perigee.

Thompson called the latter a “very near lunar perigee.”

In that position, known as perigee, the moon exerts its strongest gravitational pull, and the difference between high and low tides is the greatest.