Okay, so you know how some people believe in one God, and some people believe in many gods? Well, Muslims believe in one God too, just like Christians and Jews, but they believe something different about Jesus.
Christians believe that Jesus is the son of God, and that God is made up of three parts: the Father, the Son (Jesus), and the Holy Spirit. Muslims believe that God is just one being, without any parts or children, and that Jesus was just a prophet, like Moses or Abraham.
Muslims think that Christians and Jews are good people who believe in God, but they have a different idea about Jesus than Muslims do. Both religions think that God is all-powerful and never changes, but they see Jesus in a different way.