What the difference is between solstice and equinox?

Answer 1

Solstice is the middle of Summer and Winter, Equinox is the middle of Spring and Fall.

Answer 2

There are two solstices, summer and winter, and two equinoxes, spring and fall, each year. The longest day of the year is the summer solstice, on the 21st or 22nd of June in the Northern Hemisphere. In this case, day means the time between sunrise and sunset. The winter solstice is the shortest day of the year. At each equinox, day and night are of equal length. In all parts of the world, the day is 12 hours long on the equinox. They occur in March and September.
A solstice is the day year with the longest period of light(summer)/shortest period of (winter). An equinox are the two days in the year in which in the periods of lights and periods and darkness are exactly the same duration.
The dates are different -

Winter solstice around December 21.

Summer solstice - around June 21.

Autumnal equinox - around September 23.

Vernal equinox - around March 21.

These 4 dates start the 4 seasons.
The solstices are when most places on Earth have either the longest or shortest time between sunrise and sunset due to the Earth being at the points in its orbit at which one of the poles is at its maximum tilt toward the sun. The equinoxes are the midpoints between the solstices, on which the sun's rays are perpendicular to the Earth's rotational axis, resulting in the whole planet having about 12 hours of sunlight.
Solstice is shortest or longest day (depending on if it is winter or summer) when the sun is farthest from the equator and equinox is when day and night are of equal time everywhere on earth when the sun crosses the equator.
The solestice is day of the year with the longest period of light (the summer solstice) or the shortest period of light (winter solstice).

The vernal equinox (spring) and automnal equinox (fall) are the two days in the year in which the periods of light and periods of darkness are exactly the same duration.