What is solstice and equinox?

Equinox - When day and night are equal in length, occuring in Spring (Vernal Equinox) and Autumn (Autumnal Equinox.)

Solstice - The longest and shortest days of the year, occuring in Winter (Winter Solstice) and Summer (Summer Solstice.)

Equinoxes and Solstices are usually on the 21st of their respective months. However, the day they fall on can vary.

The summer solstice is the first day of summer. This day, June 21, is the longest day of the year.