It is called "an equinox" because on that day the Sun (nominally) spends as much time above the horizon as below the horixon all over the World.
This is a truth with modifications but close enough for general consideration.
The Sun is farthest from the equator during the solstices or when summer and winter begin.
That's called a solstice.
The 'solstices' are not events and they're not calendar dates. They are thetwo points on the map of the stars that are the farthest north and south ofthe celestial equator that the sun can ever be. The sun reaches those pointsnear June 21 and December 22 of each year,
That is called apapsis or apoapsis. For orbits that are specifically around the Sun, the term aphelion is also used.
equinoxes
equator
That's called a solstice.
Summer and Winter Solstice
The points where the sun reaches the greatest distance north or south of the equator are called The Tropics of Cancer and Capricorn. At one time the sun was in those constellations when it reached those points. It has shifted due to precession of the poles. It will be back in them in about 20,000 years.
When the sun is south of the equator, it would be winter in the northern hemisphere.
Solstice:either of the two times of the year when the sun is at its greatest distance from the celestial equator .
"Solstices" ... June 21 and December 21.
winter
a solstice is the day when the sun reaches its greatest distance north or south of the equator.
That happens at the time when the sun passes the "solstices", which are points on the map of the stars. Those days themselves are often called the solstices, but that's incorrect.
Summer and winter
That would be "Winter".
Those are the solstices, two per year, when the Sun is at maximum declination.