Next is the "official" start of Spring, which begins at 1:32 p.m. Eastern Daylight Time on Saturday, March 20. The start of Spring is defined by the Vernal Equinox ("Ver" from Latin meaning "spring," and "aequus" and "nox" combined to mean "equal night"), which is when (from our perspective on Earth) the Sun's incident solar rays are most directed at the Equator.
Earth is tilted at 23.44 degrees relative to its orbital plane, which means that as our planet orbits around the Sun throughout the year, the Sun's incident rays hit different parts of the Earth more directly.
(Image: NASA)
Thus, the Earth has seasons! Here's the perspective from Earth: