-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.
SA: The men are always effeminate both in appearence & personality, gay men didn't like it much, & unhappy endings were common. Contrary to perhaps even my own previous postings, this art is not COMPLETELY dead, some shounenai slips through the press. If it's new & fots this description, it's still shounenai.
BL: These days the men are more masculine both in looks & tude, gay men like it too, it's usually less dramatic, more sexual, & tends to end happily.
Boyslove: Ai no Kusabi, BNSH, Gravitation, Fake, Ja-Dou, Psycho Blast.
Border line: Anything that lived through both periods. For example, Patalirro, Zetsuai, & Eroica are STILL being written & have made distinct changes to fit the times.