As the Earth moves around the Sun. It also spins round on its axis. This means that different parts of the Earth are lit up at different times. When our art of the Earth is lit up it is daytime for us. As we move round, away from the Sun, it becomes dark and we can see the stars; this is night-time.
The sun appears to move across the sky, but in fact the Earth is moving around the Sun.
A star is a huge ball of hot, glowing gases, which whirls in space. All stars are made up of the same two gases, hydrogen and helium, and they shine by their own light, which is produced as a result of atomic reactions in their centre, causing great heat.
Planets are different. A Planet is much smaller and more solid than a star. It does not shine by its own light, because it is not nearly hot enough to produce that light. Instead, it shines by the light of the nearest star.
