Even though most of its people are Muslims, the country is home to numerous religions. You'll see a predominance of mosques over churches and synagogues, as you travel around Turkey.
In Turkey, 90% of the population are Muslims. Islam is the country's main religion. To be even more precise, you'll see that there are differences in the forms of Islam worshipped. Of the 90% of Muslims, 70% worship the Sunni faith. The remaining 20% are divided into several faiths - mainly Alevis but also less common idealogies such as the Sufi worshipping whirling derviches .
The Alevis are a Muslim religious minority, often treated as heretics - a 'Protestant equivalent' in Islam, if you like. Men are allowed to drink alcohol, women have rights, they don't worship in mosques and the Koran is no more than the words of an ordinary man; they don't, therefore, believe in succession. Even if there are no official statistics, estimates state that 15 million Turks are Alevi Muslims.
One unusual spectacle that you'll be able to see during your trip to Turkey, is the whirling derviches. You'll find followers of this Sufi branch of Islam in Istanbul and Konya only. To enter into communion with God, derviches twirl on the tip of their right foot. With their arms held out and their heads resting on their right shoulders, they can sometimes keep this up for 30 minutes! It's a mesmerising and fascinating sight, although today it can seem to be more of a tourist attraction than a religious ceremony.
The remaining 10% are split between Christianity and other communities, such as Greek/Turkish Orthodox or Syrian/Assyrian Jacobites.
Jews total around 35,000 and most live in Istanbul. 90% of them are Sephardic Jews. The remaining 10% percent are split between the Ashkenazi, Karaite and Marrano branches of Judaism. Even if Turkey appears today to be less cosmopolitan than in its past, its religious groups are on good terms and tolerance is encouraged.