at night it is dark on the earth and moon is visible because it is reflecting the sunlight
because the light of the sun is reflecting off of it.
The stars are basically balls of gas which emit light. They are also present in the morning but we cannot see them because of the sunlight. But at night they are visible since the earth has rotated...
It means that if you do something, someone will follow you and do the same thing, just because they saw you do it.