The Moon moves around the Earth in an elliptical orbit (the orbit has been exaggerated in this diagram). The Moon is at perigee when it is is closest to the Earth.

For the Moon or an artificial satellite body moving around the Earth in an elliptical orbit, the distance between the object and the Earth changes throughout the orbit.

The point of closest approach to the Earth is known as the perigee (from the Greek peri = near). At this point in the orbit, the object is moving at its maximum speed (Kepler’s Second Law). The perigee refers specifically to orbits around the Earth, and is equivalent to the periapsis of a general orbit.

The point of greatest separation between the Earth and a celestial object orbiting it is the apogee.