Orthodox Judaism is adhered to by around 10% of American Jews and consists of sects with various levels of engagement with modernity. The movement includes Modern Orthodox Jews, who engage fully with the modern world and may, at the leftmost streams, find ways of being more inclusive towards women and LGBT individuals. It also includes groups that may shun or minimize their exposure to secular education, have more restrictive roles for women, or have other practices designed to preserve a unique character to their way of life.
Orthodox Judaism is characterized by resting on Sabbath and holidays, observance of the Jewish dietary laws (kashrut), and observance of niddah (refraining from sexual activities (or, often, any touching or direct passing of objects) during a women’s menstrual period and for seven days afterwards). Orthodox men cover their hair with a yarmulke (kippah), and some sects wear specific types of hats, black pants and white shirt, or black outfits originally popular in Poland. Women endeavor to dress modestly — in some circles that includes wearing skirts past the knee and covering their elbows and collarbones, with various other restrictions applying depending on the community. Many Orthodox families send their children to full-time religious schools instead of public schools. Depending on the type of Orthodoxy, women may receive more or less exposure to traditional Jewish texts, and boys and girls may be taught separately.
Services in Orthodox synagogues are conducted in Hebrew, and are very similar liturgically to the services in traditional Conservative communities. Men and women sit separately during prayer, separated by a divider called a mechitzah. Different communities will divide their space in different ways, giving women more or less of an ability to see the proceedings, touch the torah during the processional, or speak publicly.
Orthodox Judaism is more opposed to interfaith marriage than other Jewish movements, and may make it difficult for people to convert if they are known to be in a relationship with a Jewish person at that time. Orthodox Judaism will not usually accept people as Jews if they have converted through other streams of Judaism, and may not accept people as Jews depending on which Orthodox rabbi sponsored their conversion.
In order to convert, someone would find a rabbi to work with, take extensive classes and make a commitment to the mitzvot (commandments), immerse in a mikveh, and have a circumcision (brit) or a ritual drawing of blood (hatafat dam brit) if they are male. Orthodox Judaism considers people to be Jews if they converted under a trusted Orthodox rabbi or if they were born to a Jewish mother.
People who marry outside the Jewish community in Orthodoxy may be ostracized, and may no longer receive communal honors, such as being called to the torah during a prayer service. In most communities, it would be extremely difficult for the partner who isn’t Jewish to play any role in the service or synagogue.