Aphelion is the point in an orbit when a planet or celestial object is farthest from the Sun.
For Earth, aphelion typically occurs around early July, at a distance of about 152.1 million kilometers from the Sun.
The opposite of aphelion is perihelion, which is when the Earth is closest to the Sun. This distance is not the main cause of seasonal changes; seasons occur mainly because of the tilt of the Earth's axis.