Every visitor to Turkey must have a valid passport and a visa, if required. 108 countries all around the World may visit Turkey without long visa procedures.
For official visa procedure visitors could also visit the official webpage of the Ministry of Foreign Affairs / Visa web page. (http://www.mfa.gov.tr/visa-information-for-foreigners.en.mfa)
E-Visa application is possible from any place. The whole process takes an average of 3 minutes.
More details can be found at www.evisa.gov.tr