You have probably noticed that when you go to sleep at night, the sun does not appear to be longer in the sky. Where has it gone?
You do not see the sun at night because the Earth is constantly rotating. When the place where you are on our planet is facing the sun, you have daytime. Throughout the day, the planet gradually turns on its axis. At the end of the day, that same place where you are on Earth is no longer facing the sun, and so you have night time. In another part of the world, it’s day time because they are now facing the sun.