The Moon orbits the Earth once each month. Every 29.53 days, we see a Full Moon as the Moon reaches the point on its orbit opposite the Sun. In this view of the Moon's orbit from above, it looks like the Earth should block any sunlight from reaching the Moon. So why isn't there an eclipse every month?
The answer is simple: the Moon's orbit is tilted by about 5 degrees with respect to the line connecting the Sun and the Earth. A view from the side reveals what happens during 90% or so all Full Moons:
