What is meant by the Christian idea of the tri-unity of God?

This idea refers to the concept that God is made up of
three separate beings that are, at the same time, one being.  This is a mystery of faith
-- that of the Trinity.

According to this idea, God is
actually made up of three "persons."   These persons are God the Father, God the Son
(Jesus) and God the Holy Spirit.  Christians believe that these three persons are
separate but that they, nevertheless, make up one God.

This
concept does not make logical sense.  It is impossible to truly understand how three
persons can yet be part of one God.  However, Christians believe that it is true and
that we cannot understand it properly because we are human beings and therefore limited
in our understanding.