<3++ means that you really really <3 someone, to the point that you almost love them. It is when you are .1 away from loving them. It is when you think about them all the time and you cant see yourself without them. When you think about them, it gives you a feeling of extreme happiness and you cant wipe the smile off your face.
Boys who enjoy yaoi (a genre in Japan that contains sexual and/or romantic relations between two men); literally translates to "rotten boy"; corresponding female : fujoshi