The six-pointed star made up of two triangles that are superimposed on each other is known as the Star of David symbol. It is also called "Magen David", meaning 'shield of David' in Hebrew, by the people of Judaism. It does not have any religious significance and is associated with the Jews, who wear the star as a part of their jewelry design. The blue Star of David symbol is the part of the flag design of Israel and is a symbol of unity.
The origins of Star of David are kind of vague. It was also used by Christians and Muslims at some point of time. It is associated with King Solomon more often than King David. The Star of David had never been mentioned in the rabbinic literature till the middle ages. After the middle ages, a deeper spirituality meaning was associated with the star by Kabbalists.
The Magen David was first used as a Jewish symbol in Prague, Czechoslovakia, in 1354. Jews were given the right to have a flag, by Emperor Charles IV. The people chose the double triangle star, as their symbol. When the Emperor was welcomed to the city in 1500s, they displayed the star on their banners.
In the 1600s, Emperor Ferdinand II ruled over Prague and the city was attacked by Swedish forces. The Jews defended the city for the emperor, and as an appreciation they were given the right to adopt a coat of arms. This was an exceptional honor, as it was only bestowed to the people from noble families.
It is still dicey as to why the six-sided star was chosen as the Jewish symbol. There are certain theories regarding the Star of David symbol, like one that says Alexander the Great had conquered Jerusalem. The Jews had to fight for their religious freedom and the shields designed for the solders had the six-pointed star. One of the stars stood for King David and the other star symbolized his decedent, the Messiah.
Soon, it became a symbol of the Jews and was used as an architectural decoration for Jewish buildings. Adolf Hitler during the World War II, forced the Jews to wear a yellow Star of David as a 'badge of shame'. The star was yellow, as the color was associated with the negative and stigmatizing way of the Jews.
After the war this symbol of shame was converted into a symbol of honor and respect. The Zionists gave a national significance to the star during the founding of Israel and gave it a place on the white banner with two horizontal blue lines with the Star of David in the center, thus, making it the national flag of Israel. Even today, you see the Star of David fluttering on the national flag as a sign of hope and protection for every Jew and anyone who seeks for it.
There are many symbolic meanings attached to the Star of David. The triangle within the star that points upwards is a symbol of good deeds that reach the heaven and attract goodness to the world. This attraction of goodness is symbolized by the downward pointing triangle.
Some Kabbalists say, the six points represent the absolute rule of God over the universe in all directions. The north, south, east, west, up and down are all under one God's rule. It may also symbolize the dual nature of good and evil and should be used to protect one against evil spirit.
The other meaning of the Star of David indicates that the overlapping stars represent the relationship between God and Jews. The star pointing upwards represents God and the star pointing downwards represents people on earth. The six sides and the center represents the six working days and hexagon at the center represents Sabbath. It may also mean the twelve sides on the triangle that represent the Twelve Tribes. You can read more on famous Jews.
So, in the end I conclude there is just one meaning of the Star of David, that one can staunchly promote. It is a symbol of unity and hope for Jews and a form of identification for the followers of Judaism. Just as the cross symbolizes Christianity and the crescent moon represents Islam religion, Star of David is a symbol of Judaism. There is one thing for sure, the star represents the hundreds and thousands of years of struggle that the people of Judaism have been through. It is a sign of rich religious history and a sense of pride for the Jews.