The Sun, Moon and stars
Earth spinning gives day and night, and the Moon looks different each night because we see different amounts of its sunlit half.
A worked example
At new moon the lit half faces away from us. About two weeks later we see all of it, and the whole cycle back to the start takes roughly a month.
The mistake people actually make
The Moon makes no light of its own and does not change shape. The Sun is a star like the ones you see at night, and looks far bigger only because it is so much closer.