Orthodox Judaism includes more religiously stringent forms of Judaism. It is not a single movement. It includes diverse religious outlooks and practices.
Orthodox movements include Modern Orthodox, ultra-Orthodox, and Hasidic. These movements share a few common principles.
Generally, Orthodox Judaism holds that G-d revealed the Torah to the Israelites at Mount Sinai. It also holds that the Torah and rabbinical tradition are clear accounts of the divine rules that all Jews are required to follow.
It is very conservative on how current rabbis may decide what the law is in new cases. It mostly resists the idea that law can change in response to changing social circumstances.
B'nai Israel Synagogue, 27 Lloyd Street, Baltimore, MD; Photograph by Eli Pousson via Wikimedia Commons, CC0.
