Баха Валад - Маариф (Миниатюра).jpg
Haci Bektas-i Veli, picture from Wikipedia

The “Republic of Turkey Ministry of Culture and Tourism” has an article on the Turkish Cultural Foundation’s website that briefly explains the origin of dervishes before focusing on Haci Bektas-i Veli (“a great Turkish thinker”). The brief explanation of dervishes alone is worth the click.