The word dervish covers wildly different practice depending on which order is doing the naming. In the Mevlevi order, founded on Jalal al-Din Rumi's teaching in Konya, a dervish is a novice completing the cile, a rigorous roughly thousand-and-one day training period of menial service and instruction inside the lodge, that culminates in participation in the sema, the turning ceremony that gave English its image of the whirling dervish; the practice is a formal, closely supervised devotional discipline, not a public performance, whatever it has become in modern tourist contexts.
The Rifa'iyya, founded by Ahmad al-Rifa'i in the Iraqi marshlands, produced the dervishes nineteenth century Western travelers called howling dervishes, known for public demonstrations of ecstatic states under a sheikh's direct supervision, including handling fire or piercing the body with skewers, offered as visible evidence that the practitioner's trance genuinely suspended ordinary sensation. Trimingham records the practice as controversial even within Islam, tolerated by some sheikhs as legitimate proof of spiritual attainment and condemned by others as theatrical excess.
The Bektashi order took yet another path, building its whole identity around the dervish lodge, the tekke, as a center of communal and often unorthodox religious life, historically tied to the Ottoman Janissary corps until both were suppressed together in 1826, after which Bektashi dervish lodges survived chiefly in Albania and the Balkans.