The ultimate and final truth is, "God is one" But we just call him with different names on different part of Earth. Same is true in case of religion also. For example, "River, pond, waterfall, sea and so on... Names and forms of them is different But they all contains only one thing inside it and that is water. Similarly, Hinduism, Christianity, Muslims and so on... Names and rules are different but all contains only one thing inside it and that is Truth."