How day and night occurs?

Unsurprisingly we live on a SPHERICAL object that orbits a host star called Sol or the sun. As we orbit the star, our planet, Earth, rotates on its own axis which completes one rotation within 24 hours.

As Earth turns one side is exposed to the light of the sun, daylight. The other side, engulfed in temporary darkness for approximately 12–13 hours until the Earth spins that side back into the light.

This is also the reason that nights are colder, the dark side of the earth is no longer exposed the the heat of the sun.