So, at the end of the day, while solstices and equinoxes are related, they happen at different times of the year. Just remember that solstices are the longest and shortest days of the year, while equinoxes occur when the day and night are equally as Long.
The two equinoxes occur around March 20–21 and September 22–23, marking the onset of both spring and autumn. During the equinox, the sun crosses the plane of Earth's equator, making nighttime and daytime (roughly) equal length all over the world
The seasons on Earth change because the planet is slightly tilted on its axis as it travels around the Sun. This means different points on Earth receive more or less sunlight at different times of year