Christianity has a very simple central premise: we believe that God
loves humankind so much that he became man as Jesus, died for our sins, and came back to life, thereby conquering
sin and death. He thus reached out to us, because we are incapable of
reaching out to him. Anyone who trusts in Jesus will have eternal life.
Christians believe that most of the Jewish Bible
(what we call the Old Testament) foretells this; the main theological
fight between Christians and religious Jews is over the identity of
the Messiah (Hebrew Moshiach; Greek "the Christ"). We think he
already came, with a mission different from the one they expected.
I think Christianity
is controversial ``around here'' (cyberspace) partly because it's the
majority religion in the West, partly because of the fights between
scientists and Christians (based on misunderstandings all around), and
partly because conservative politicians have tried to politicize the
religion:
As one example of these kinds of misunderstandings, you sometimes hear a
quote attributed to Tertullian ``I believe it because it is
impossible''. This turns out to be a misquote, and taken out of
context at that!
See point four in this
list of Tertullian quotes.