Wikipedia
Koryo-saram ( Cyrillic: Корё сарам, Hangul: 고려사람) is the name which ethnic Koreans in the post-Soviet states use to refer to themselves. The term is composed of two constituents: " Koryo", which refers to Korea from the years 918 AD to 1392 AD, and "Saram", which means "Person". Approximately 500,000 ethnic Koreans reside in the former Soviet Union, primarily in the now-independent states of Central Asia. There are also large Korean communities in southern Russia (around Volgograd), the Caucasus, and southern Ukraine. These communities can be traced back to the Koreans who were living in the Russian Far East during the late 19th century.
There is also a separate ethnic Korean community on the island of Sakhalin, typically referred to as Sakhalin Koreans. Some may identify as Koryo-saram, but many do not. Unlike the communities on the Russian mainland, which consist mostly of immigrants from the late 19th century and early 20th century, the ancestors of the Sakhalin Koreans came as immigrants from Gyeongsang and Jeolla provinces in the late 1930s and early 1940s, forced into service by the Japanese government to work in coal mines in Sakhalin (then known as Karafuto Prefecture) in order to fill labour shortages caused by World War II.