It takes one year for the Earth to move around the sun. It turns on its axis each day. The part facing the sun is lit and heated by it. On one side it is day, and on the other night. However, the lengths of the days and nights change during the year. You have heard of the longest and shortest days. This doesn't mean that a day and night together don't add up to 24 hours.

In the Northern Hemisphere, north of the equator, the longest day is in the middle of the summer. The sun goes behind the horizon for only a few hours. The shortest day is in the middle of winter. The sun only rises above the horizon for a short time. It is dark until late in the morning and by early in the evening. The night is long.
South of the equator, in the Southern Hemisphere, the opposite happens. If it is summer in the north, it is winter down in the south. And, of course when it's summer in the south, it's winter in the north. In Africa, Christmas is celebrated in the height of summer. Of course, dark clouds hid e the sun from us, sometimes all day long. When the moon passes between the sun and the Earth, it causes an eclipse of the sun. This can be partial or total.