People often ask us the reason behind the traditional Jewish yarmulke (skull cap), also called a kippah (Hebrew for covering).
The following information comes from a catalogue that sells a variety of kippot (plural for kippah):
The sources for wearing kippot (Jewish skullcaps) are found in the Talmud [rabbinical commentary, also known as the Oral Law]. In tractate Shabbat 156b it states, 'Cover your head in order that the fear of heaven may be upon you. 'As well, in tractate Kiddushin 32a it states, 'Rabbi Huna the son of Rabbi Joshua never walked 4 cu [protected]bits (2 meters) with his head uncovered. He explained: "Because the Divine Presence (Shekhina) is always over my head."' While there is a minority opinion that wearing a kippah... is a Torah commandment, most... agree that it is merely a custom.
The prevailing view among rabbinical authorities is that this custom has taken on the force of law (Shulkhan Arukh, Orach Chayim 2:6). From a strictly talmudic point of view, however, the only moment when a Jew is required to cover his head is during prayer (Mishneh Torah, Ahavah, Hilkhot Tefilah 5:5).
"Reasons given for wearing a kippah today include: recognition that God is 'above' humankind; acceptance of the 613 mitzvot (commandments) and identification with the Jews.
"Some have a custom of wearing two head coverings, typically a kippah and a cap on top, for Kabbalistic reasons; the two coverings correspond to two levels of intellect, or two levels in the fear of God. The High Priest of the Temple in Jerusalem, the Kohen Gadol, also used to wear a woolen kippah under his priestly cap (Talmud Chulin 138a)."