Question: "What is the Star of David and is it biblical?"
Answer: There is no reference to the Star (or shield) of David in the Bible. There are several rabbinical tales as to the origin of the Star of David. These range from the star being the shape of King David's shield, to being the symbol on King Solomon's signet (seal) ring, to being an invention of Bar Kokhba, the Jewish leader who led what is known as the Bar Kokhba revolt against the Roman Empire in A.D. 132. Mekubbalim (followers of Kabbala) claim that the symbol has magical powers. There is no explicit historical or archaeological support for any of those claims.
The star consists of two intertwined triangles: one pointing up to God and the other pointing down to man, symbolizing the relationship between the two—"the interpenetration of two realms" (source: Franz Rosenzweig, Star of Redemption, 1912). The six points are said by Rosenzweig to represent two triads: creation, revelation, and redemption, along with God, Israel, and the Gentile world. These are alternatively characterized by Eder as representing the six aspects of the Divine Spirit as per Isaiah 11:2 (Eder, The Star of David, p. 73). Kabbala teaches that the six points indicate the extent of God’s sovereignty (north, south, east, west, up, and down). The star has 12 lines about its perimeter, possibly representing the 12 Tribes of Israel.
The earliest archaeological finds bearing the sign are a Jew's tombstone in Tarentum, Italy, dating to the 3rd century and its appearance on the wall of a 6th-century synagogue within the borders of ancient Israel. It was used quite infrequently until its official adoption by Jews in Prague in the 17th century and later by the Zionist movement in 1897. Nazi Germany used the symbol to mark Jews within their borders, and after much debate, it came to be used on the national flag of reconstituted Israel in 1948. As a result, the Star of David is now universally recognized as a representation of Judaism, Israel, and Zionism.