the earth moves round the sun, and the moon moves round the earth. when our part of the earth turns to the sun, it is day. when our part of the earth turns away from the sun, it is night.
the sun is bigger than the moon. but sometimes the moon looks bigger than the sun, because it is much nearer to the earth.
the sun is very bright. it gives very strong light. the moon looks quite bright, too, but it doesn’t give any light at all. the light from the moon comes from the sun.

the moon looks much bigger and brighter than the other stars. but in fact many stars are much bigger and brighter than the moon. they look smaller than the moon because they are farther away from the earth.