Christians believe in one God, so how exactly does each part of the Trinity contribute to God? Christians believe in one God, so how exactly does each...

The
first post does a good job in explaining the general concept of the Trinity.  Being Roman
Catholic, I just thought I would throw out Saint Patrick's awesome (and easy to understand)
explanation as well.

The Trinity is comprised of God the Father, God the Son
(Jesus Christ), and God the Holy Spirit (or the Holy Ghost).  Three persons, ... one God.  Saint
Patrick told the people of Ireland that the best way to understand this Triune God was to look
at their very own shamrock.  A shamrock, being a little plant that grows all over Ireland, has
three leaves protruding from its one stem.  Of course, it is still only...