Moon has a very thin atmosphere made up of mostly Argon, Helium and Hydrogen. This means that its surface is unprotected from cosmic rays, meteorites and solar winds. It has a wide variation of temperature that goes from very hot at 107 °C during the day to very cold down to -153 °C at night.
Lack of atmosphere also means that sound couldn't be heard on the Moon and the sky appears black even during the day. Here's a little science quest for you: Find out why our sky is blue in color during the day?
Moon is thought to have been formed roughly 30 to 50 million years after the birth of Solar System. It is theorized that a Mars-sized object named Theia smashed into proto-Earth (early molten Earth) blasting off materials that later accreted into Moon. However, a clear explanation to what led formation of the Earth-Moon system is not understood yet.