The term "bf" commonly stands for "boyfriend" or "best friend." It is often used as a shorthand or abbreviation in English for these meanings. "BF" can mean a romantic partner (boyfriend) or a very close friend (best friend) depending on the context.
Additionally, "BF" can refer to other things but these are the most widespread and common usages in everyday language. If you meant something else by "bf," please provide more context for a precise explanation.