Judaism
Around the 1st century CE, there were several small Jewish sects: the Pharisees, Sadducees, Zealots, Essenes, and Christians. After the destruction of the Second Temple in 70 CE, these sects vanished. Christianity survived, but by breaking with Judaism and becoming a separate religion; the Pharisees survived but in the form of Rabbinic Judaism (today, known simply as "Judaism"). The Sadducees rejected the divine inspiration of the Prophets and the Writings, relying only on the Torah as divinely inspired. Consequently, a number of other core tenets of the Pharisees' belief system (which became the basis for modern Judaism), were also dismissed by the Sadducees. (The Samaritans practiced a similar religion, which is traditionally considered separate from Judaism.)
Orthodox Judaism
Orthodox Judaism is not a centralized denomination. Relations between its different subgroups are sometimes strained, and the exact limits of Orthodoxy are subject to intense debate. Very roughly, it may be divided between Ultra-Orthodox or "Haredi", which is more conservative and reclusive, and Modern Orthodox Judaism which is relatively open to outer society. Each of those is itself formed of independent streams. They are almost uniformly exclusionist, regarding Orthodoxy as the only authentic form of Judaism and rejecting all competing non-Orthodox philosophies as illegitimate. While adhering to traditional beliefs, the movement is a modern phenomenon. It arose as a result of the breakdown of the autonomous Jewish community since the 18th century, and was much shaped by a conscious struggle against the pressures of secularization and rival alternatives. The strictly observant and theologically aware Orthodox are a definite minority among all Jews, but there are also numerous semi- and non-practicing persons who are officially affiliated or personally identifying with the movement. In total, Orthodox Judaism is the largest Jewish religious group, estimated to have over 2 million practicing adherents and at least an equal number of nominal members or self-identifying supporters.