Whenever you see "-gee" in the description of a point in an orbit,
you know it's talking about an orbit of the Earth. You see the same
piece of a word in "geology" and "geography". "Geometry" began
as the study of measuring places on the Earth, so that you and your
neighbor could agree on where your field ends and his begins, and
if you wanted to buy part of his field from him, the two of you could
go outside, do some measurements, and agree on what area you're
paying him for.
"Perigee" and "apogee" are the points in the orbit of the Moon, or a
TV satellite, or the International Space Station, where the orbiting body
is nearest or farthest from the Earth. "Perigee" is the lowest/nearest point.
"Apogee" is the highest/farthest point.
If the description has "-helion" in it instead of "-gee", then it's talking about
an orbit around the sun, like points in the Earth's orbit. The "-helion" comes
from the Greek word "Helios" for the Sun.
Earth is at perihelion during the first few days of January, and at aphelion
during the first few days of July. (That's right ... nearest to the sun in January,
and farthest from the sun in July.)
