It's a story where two male characters (usually the main characters) fall in love. There are a lot of standard tropes. which most follow. They're actually shows that have a high female teen following in those countries. They seem to have a fascination with the idea of two handsome guys falling in love! Many TV and movie stars in those countries get their 'big break' through starring in a main or major role in one of these types of drama.

There's rarely any actual guy-on-guy action, at least in those I've seen so far, though some people have told me otherwise, especially in some Thai stuff apparently. They're mainly about the lead-up to becoming a couple, with some holding hands and a kiss or two as the highlight.

If you want to see a sample, and also want a laugh, I recommend "I Became the Main Role of a BL Drama", which is in many ways a parody of such shows, incorporating nearly every trope that's out there. It's extremely funny. At least I found it so.

Don't feel stupid, I've been here for 20 years, and I don't know what it means.