The creation of the moon has many theories. The leading and most agreed upon theory is of a planet that was bit smaller than Mars, it has sweetly got a name too called Thea.
Thea struck against a hot and molten Earth in the earliest stages. This impact was so massive it tilted our planet to an angle 23.5 Degree. That tilt gives us seasons and weather patterns. This impact also started our rotation, thus give us a day and night.
On the other hand, the impact gave us Moon, a really really large satellite. It has the biggest ratio for the planet size to the satellite, ever found. That gives us weather currents, tides and made nights less dark.
The primary reason to come to this conclusion is actually very simple. The composition of all planets is different, however, Moon's composition is very similar to our own. It is actually born out of the "rocky" marriage of Earth and Thea.