Answer 1:
Very interesting question. A lot of people
confuse the phases of the moon with solar and
lunar eclipses. The phases of the moon are
strictly due to how much light is illuminating the
face of the moon that we can see at a given time.
An eclipse occurs when the sun, moon, and earth
are in perfect alignment. When the moon is
between the sun and Earth, you get a solar eclipse
- because the moon is so much closer to us than
the sun, the moon appears as big as the sun and
can block out the sun. When the moon is behind the
earth, directly in the earth's shadow, you get a
lunar eclipse (like a dimming of the moon).
Because the earth's orbit and the moon's orbit are
on different planes, they do not always perfectly
line up with the sun. That is why you can have a
new moon without having a solar eclipse, and a
full moon without having a lunar
eclipse. Here is a link to a web page that
has some diagrams to help visualize this
stuff. eclipseIn
particular, look at the first diagram of the
phases of the moon, and the diagrams about 3/4 of
the way down the page that shows the moon's
orbital plane and the earth's orbital plane
(called the ecliptic since the orbital path
is an eclipse). You can see that there will be at
least two eclipses during the year - when the two
orbital planes intersect.
Because both the moon and earth actually wobble
like a top spinning on the ground, their orbits
change slightly and there can be more than two
intersections of the orbital planes. This also
makes it so that eclipses do not always occur on
the same date every year. | 
