Karelian is a dialect of, or a language closely related to, Finnish. It belongs to the Finno-Ugric languages, and is chiefly distinguished from standard Finnish by the lack of influence from modern 19th and 20th century Finnish.
Karelian has three main dialects, Karelian Proper, Olonets and Ludic. The latter is sometimes classified as a dialect of Veps.
Attempts to standardize Karelian with a Cyrillic alphabet were unsuccessful, and today the Karelian republic (of the Russian federation) consider Karelian a dialect of Finnish, why Finnish is one of its official languages. However, it could also be argued it should be considered a separate language because of its geo-political location within the boundaries of another state. The conclusion might be that Karelian has a similar relation to Finnish, as has Finland-Swedish to Scandinavian Swedish.