If a solar eclipse occurs when the Moon is at the far point in its orbit, the Moon will not cover the Sun entirely. A thin ring, or annulus, of sunlight will be visible around the Moon. This kind of eclipse is called an annular eclipse. A lunar eclipse occurs when the Earth passes between the Moon and Sun, viz. Sun Earth Moon Lunar eclipses are either total or partial, depending upon whether the Moon moves completely into the Earth's shadow or not.
Lunar eclipses are always safe to view.
Eclipses do not happen once a month because the Earth's orbit about the Sun and the Moon's orbit about the Earth are not in the same plane. Only when the three bodies are in the same plane can an eclipse occur. The total number of eclipses, both lunar and solar, never exceeds seven in a year.