Judaism is the ancient religion of Israel carried forth by their descendants. The name derives from Judah - the principle faithful kingdom after the division of the kingdom of David. Judaism is a monotheistic religion based upon principles and ethics embodied in the Hebrew Bible (Tanakh), as further explored and explained in the Talmud and other texts. According to Jewish tradition, Judaism began with the Covenant between God and Abraham.
Modern Judaism is generally divided into four denominations: Orthodox Judaism, Conservative Judaism (known as Masorti Judaism outside of the United States and Canada), Reform Judaism (called Liberal or Progressive in many countries), and Reconstructionist Judaism. Each denomination believes in the God of the Old Testament but, of course, does not believe that Jesus of Nazereth was the Messiah, much less the Son of God.