Jews who worship any entity worship God, aka Hashem. As you’re probably aware, we don’t have godheads, saints, or other figures worthy of worship — just God.
“Bar” means son, “bat” means daughter and “mitzvah” means commandment or law. So a bar or bat mitzvah is literally a son or daughter of commandment (i.e., one who is expected to uphold the commandments of the Torah).
The short answer is that the Torah is the first five books of Moses: Bereishit (Genesis), Shemot (Exodus), Vayikra (Leviticus), Bamidbar (Numbers), and Devarim (Deuteronomy).