I can explain you the meaning of BL, GL, and SL. The words are abbreviations that used in the meaning of Boy loves, Girl loves and Straight love And these words just some kind of genres that usually used in movies, books, or scenarios. BL has a romantic scenario between two boys, GL has a romantic scenario between two girls, and SL is a romantic scenario between a girl and a boy. Ask any more questions about these and also I can suggest you series, movies or books in these genres, just ask me (;