At the center of it all is the Sun. It takes the Sun 25 days to spin, or rotate, completely around.
The Earth, which is the third planet from the Sun, takes 24 hours to rotate. This is what causes day and night. As the Earth rotates, it also moves, or revolves, around the Sun.
The Earth’s path around the Sun is called its orbit. It takes the Earth one year, or 365 1/4 days, to completely orbit the Sun.
As the Earth orbits the Sun, the Moon orbits the Earth. The Moon’s orbit lasts 27 1/2 days, but because the Earth keeps moving, it takes the Moon two extra days, 29 1/2, to come back to the same place in our sky.