Jehovah is the Anglicised (i.e. King James) translation of the tetragrammaton, or sacred four letters denoting the name of God. In the Jewish tradition, the name of God is never spoken, and is denoted by the four letters YHVH. Today, God's name is translated in the Catholic/Christian tradition as Yahweh, and still in some protestant traditions as Jehovah. In the Rastafari tradition God's name is Jah.
YHVH is the God of the Jewish Torah/Tanakh and the Christian New Testament. History points to the Hebrew patriarch Abraham as the father of monotheism -- the belief in One God, and Abraham is thus counted as the father of Judaism, Christianity, Islam, and all derivative monotheistic religions.
"Jehovah" is a name used for God in The Bible, particularly in the Old Testament. It is commonly associated with the God of the Israelites and is used by some Christian denominations as a way to refer to the one true God.