Wearing of a head covering Kippot, yarmulka, skullcaps, kippah  for men was only instituted in Talmudic times  The first mention of it is in Tractate Shabbat, which discusses respect and fear of God. Some sources likened it to the High Priest who wore a hat (Mitznefet) to remind him something was always between him and God. Thus, wearing a kippot makes us all like the high priest and turns us into a "holy nation." The head covering is also a sign of humility for men, acknowledging what's "above" us (G­d).
 

Many Ashkenazi rabbis acknowledge that wearing Kippot covering at all times was once considered an optional midat chasidut (pious act), but, today, full­time head covering is the norm except under extenuating circumstances. Sephardic communities generally did not have the custom of wearing a kippah all the time.
 

Some diaspora Jews leave off the yarmulkas at school, work, or when testifying in court, because of real danger or uneasiness in appearing in the secular world with an obvious symbol of Jewishness.
 

In Israel wearing Kippot also has a social significance. While wearing a kippah shows that you are somewhat religious, not­wearing one is like stating, "I'm not religious." The style of kippot in Israel can also indicate political and religious affiliations. Classical orthodoxy uses a large, smooth, black one shaped like a bowl. Many Hasidim use large black felt or satin, and a "rebellious son" may wear a slightly smaller black SkullCaps to show his independence while remaining in the Classicist camp. Another play on this rebellion is to wear  knitted black kippot. This is also usually used to confuse people as to where you stand.
 

In Bukhara and the Caucasian Mountains the use of  large brightly woven yarmulkas is common. It is similar in shape to a cantor's yarmulka without the peak. This custom can also be found in other Sephardic communities.
 

Knitted kippot typically signify that you are part of the Nationalist Zionist camp. A larger full headed knitted kippah would signify the Mercaz Harav branch of the movement that produces many of the leading rabbis within the Religious Zionist section, although many rabbis who teach at these institutions wear the traditional large black kippot.