The EU has a common visa policy for short stays (up to 3 months), which is applied through the Schengen visa scheme. Visas for visits exceeding that period remain subject to national procedures
Citizens from some non-EU countries are required to hold a visa when travelling to the Schengen Area. Turkey is among the countries for which that visa is required. However, Member States may exempt Turkish citizens from the above visa requirement holding diplomatic passports, service/official passports or special passports.
Generally, a short-stay visa issued by one of the Schengen countries entitles its holder to travel throughout the 26 Schengen countries for up to 90 days in any 180-day period.
The EU's common list of countries whose citizens must have a visa when crossing the external borders and a list of countries whose citizens are exempt from that requirement are set out in Regulation (EU) 2018/1806.
Information about visas for travelling to Turkey is available through this Turkish government webpage.
The EU launched the Visa Liberalisation Dialogue with Turkey in December 2013 which is still ongoing.