Boys' love (BL) is the common term used by the publishing industry to categorize works focusing on male/male relationships marketed at women. Historically these works were referred to as June, but most commercial works are now called BL. It is used as an umbrella term for:
-both commercial and amateur works
-works with no sex
-works with sex
-doujinshi about adolescents with little or no sex
-works in all types of media - manga, anime, novels, games, and drama CDs
-characters of all ages (not limited to 'boys')
-related terms such as yaoi, shounen ai, tanbi, June, and original June
While early fans of BL were probably fans of doujinshi, most Japanese fans on the net these days appear to be fans of commercial BL work - there are over a hundred such works published every month, more than two-thirds of them novels and the rest manga. BL novels are immensely popular - the number of novels published each month outnumbers pmanga] tankoubon by about 2 to 1.
Gravitation is a great example of BL.
Mixed with man love, creates NAMBLA