I'm not quite sure what you mean. ett departement is a government department in Sweden, aka a ministry in English. In Finland, they are called ministerier (also an ett word).
Administrative districts in Sweden today include län, kommuner, in some cases regioner. You can read more about those in this Wikipedia article.
The word en avdelning on its own is most likely a department of a company, hospital or government agency. But it can also be e.g. a part of a book or article.
Is it related to a department in a company? In English we'd say, "That's not my department," if someone were to ask us to do something like file some papers but it's not in our job description to do that. Or like a department store where mens and ladiea clothes are separate departments?