JDM stands for "Japanese Domestic Market" and refers to auto parts originally made for the Japanese market. In the context of automobiles and tuning, JDM refers to Japanese import vehicles manufactured and sold in Japan, which often feature special and exclusive parts or features. JDM cars are usually special and limited production, making them very popular with car collectors and enthusiasts. Often considered high quality and innovative, JDM parts are often used by auto tuners and racers to improve the performance and appearance of their vehicles.
In the tuning scene, JDM is also referred to as vehicles from Japanese manufacturers.