Three (3) Parts of the Trinity

The Three Parts of the Trinity are as follows:

    1) Father

    2) Son

    3) Holy Ghost

The Christian God is considered, by those who consider themselves to be Christians, to consist of Three parts as listed above.  This is very similar to the beliefs held by many of the ancient so-called Pagan Religions.

Christianity seems to consider these Three Gods to be the same as one God. I find this to be at least somewhat confusing for a Religion that claims to be monotheistic.  I do not understand the need for the One Supreme Being to be trisected into Three parts.

Is the Great Spirit of the American Indians the same as the Holy Ghost?