"schwul" is a German term, which means "gay" or "homosexual" in English. It refers to content that features or caters to gay men, such as homosexual activity between two men or any theme related to the gay male community. This tag helps adult viewers who are interested in this specific category of pornographic material to easily find and identify relevant content.
For a more accurate translation, it is written as "schwul" in German, and pronounced as "shvool" in English.