A kippa, kippah or yamaka is a brimless cap or skullcap, made of cloth. Kippas (kippot in Hebrew) are worn by Jews to fulfill the customary requirement held by Orthodox authorities that the head be covered at all times.
The tradition to wear a kippa is not derived from the Bible itself. It is a custom which evolved as a sign of the Jewish recognition that there is someone “above” who watches every act.
Most synagogues and Jewish funeral services keep a supply of kippas ready for the temporary use of visitors who have not brought one themselves.
Prior to Pic-A-Kippa bursting onto the kippah scene, the only way kippa companies were able to customize a kippah was by printing an image or a logo onto a small part of the kippa, on one quarter of it. The way yarmulkes are made is by essentially taking four quarters and seeing them together. Then came along Pic-A-Kippa and turned the entire kippa on its head so to speak.