The kippah (literally dome) is the Hebrew word for head covering, called in Yiddish as Yarmulka.
Jewish law (halakha) requires men to cover their heads as a sign of respect to God when they are praying, studying Torah, reciting a blessing, or entering a synagogue.
This practice dates back to biblical times, when priests in the Temple covered their heads to do their work.
Traditionally, Jewish men wear a kippah at all times as a symbol of recognition and submission to a "higher" entity. Although the Talmud does not record it as a law, over time it became a universally accepted custom, to the point that many halakhic authorities maintain that it is obligatory. Therefore, a person should not even sit without a kippah. Young boys are also taught to wear a kippah at all times.