While it may sound like a tourism brochure cliché, Turkey really is a curious mix of the west and the east—you may swear you were in a Balkan country or in Greece when in northwestern and western parts of the country (except that Byzantine-influenced churches are substituted with Byzantine-influenced mosques), which are indeed partly inhabited by people from Balkan countries, who immigrated during the turmoil before, during, and after WW1, while southeastern reaches of the country exhibit little if any cultural differences from Turkey's southern and eastern neighbours. Influences from the Caucasus add to the mix in the northeast part of the country. It can be simply put that Turkey is the most oriental of western nations, or, depending on the point of view, the most occidental of eastern nations.
Perhaps one thing common to all of the country is Islam, the faith of the bulk of the population. However, interpretation of it varies vastly across the country: many people in northwestern and western coasts are fairly liberal about the religion (being nominal Muslims sometimes to the point of being irreligious), while folk of the central steppes are far more conservative (don't expect to find a Saudi Arabia or an Afghanistan even there, though). The rest of the country falls somewhere in between, with the coastal regions being relatively liberal while inland regions are relatively conservative as a general rule. The largest religious minority in the country are the Alevites, who constitute up to 20% of the population and who subscribe to a form of Islam closer to that of the Shiite version of Islam and practice Shamanistic rituals of ancient Turks. Other religious minorities—the Greek Orthodox, Armenian Apostolic, Jews, Syriac Oriental Orthodox, and Roman Catholics, the latter of whom mainly settled in Turkey within the last 500 years from Western European countries—once numerous across the country, are now mostly confined to the large cities of Istanbul and Izmir, or parts of Southeastern Anatolia in the case of the Syriac Oriental Orthodox. Despite its large Muslim majority population, Turkey officially remains a secular country, with no declared state religion.