The moon is a natural satellite of the earth which rotates at 10 mph, compared to the earth's rotational speed of 1000 mph. Its rotation is synchronized with earth which means the same side is always facing us, therefore only 59% of the surface of the moon is visible from earth.
The moon was formed around 4.6 billion years ago and its surface is covered in extinct volcanoes, lava flows and craters as well as impact craters from later meteorites. As the moon cooled down the lava solidified, leaving large beds of lava which scientist describe as seas; Apollo 11, which put the first humans on the moon, landed in the area called “the Sea of Tranquillity”. Some of these craters and lava flows are visible from earth with the naked eye.
Although, viewed from earth, the moon looks perfectly spherical it is, in fact, oval in shape. Scientists believe it is due to the gravitational pull between the moon and earth.
The phases of the moon are due to the shape of the illuminated or sunlit area of the moon as seen from earth. These luna phases change cyclically as the moon orbits the earth, depending on the positions of the moon and sun relative to the earth.