What do the crescent moon and star mean?
This combination is seen in the flag of Turkey. There are many imitators, but they are just that...
Due to the 1,000 year fight of Muslim Turk and Christian Europe, the symbols have come to be mistakingly representative of Islam by Europeans and now the world. The Crescent Moon and Star (Sun during the Ottoman Empire) are ancient Turkish celestial symbols of power originating from the Turkish, ancestoral lands of Siberia and Central Asia.
Its origins are not Arabic or Persian and it can not be Islamic due to the strict, religious doctrines forbiding the usage of any symbols or the painting/drawing/sclupting of human faces... these very important religious facts are disregarded today by those trying to claim the Moon & Star as their own today.
Needless to say, the origins of the Crescent & Sun/star are in fact Turkish from ancient times, pre-Islamic. The Turks believed in Shamanisim and more importantly the one supreme Sky God (Tanri) along side others gods like that of the Moon & Sun, when they roamed nomadicaly on horseback in the steppes of Siberia & central Asia.
In the 10th century, the Turks accepted Islam on their own will and conquered the Middle East. Witin a few centuries, the Turks became extremely powerful and strected an empire from the gates of Vienna, Austria, Russia all the way to Spain in the west. They brought into Islam their own free spirit, dynamizm, Turkish culture, superstitions and serious beliefs as well. This is the origin of how the Crescent Moon & Star came into the Islamic world.
The importance of the celestial bodies can be seen in many Turk epics, poems, songs, names etc... One quick example is that of the legendary leader of the Western Turks, Oguz Khan, named his first 3 born Sun, Moon, & Star emphasizing the importance of the celestial objects to Turks. The founder of the Ottoman Turkish empire, Osman, had a dream in which he invisioned a Crescent Moon stretching over the Earth, he took it as a good sign and made it the symbol of his dynasty. Where ever a Turkish army met with a Euro-Christian one, of course it would be seen that the Turks used a Moon and Europeans assumed that this was the symbol of Islam used by Muslim people. [this was wrong of course, as I said no symbols are allowed, but Turks quite often incorporated their own beliefs and free spirit regarding the religion]
So, over the 1,000 year fight of Muslim Turk and Westerners, the symbols have come to be mistakenly representative of Islam by Europeans and now the world. The Crescent Moon and Star are ancient Turkish celestial symbols of power originating from the Turkish, ancestral lands of Siberia and Central Asia. You see for a 1000 years Turks were the warriors, the leaders of Islam so it is not unusual that our symbols have been adopted by many present-day countries that are by a majority Muslim. But it doesn't mean that the symbols are Islamic or Muslim. Unfortunately, this confusion will most likely never be cleared up. It is very deep in the minds of the world, even the Muslim world.
Interesting note: The representative color of all Turks in the world is Skyblue or Turquiose, but we have also ascribed color to the four cardinal directions (North=Black, East=SkyBlue, South=White, & West=Red). Therefore, the Red background is used to indicate that we are the most geographically western of our family. (Over time and among the folk, the color has also come to represent the Turkish blood shed over the centuries of warfare.)
The crescent moon and star in Islam means nothing rather it's a cultural thing which a lot of Muslim majority countries adopted in homage to the Ottoman and Mogul empire.
However, outside of Islam it just represent pagan gods specifically Greek, Turk, Persian and mongol.