What is a "brown-bag talk"?

In past posts, and the recent Unit testing SharePoint post, I have mentioned "brown-bag talks."  This has spurred emails from non-native English speakers asking me what in the heck a brown-bag talk is...

I am not sure if this is a Microsoft term, or a wider industry term (I think I remember it from my pre-MS employment, but that was a long time ago).  Either way, it is a meeting over lunch where one person presents something they found interesting.  The p&p dev team has organized a series of lunches every couple of weeks to talk about new and interesting technologies we are working with, and I have also seen brown-bag talks that cover just about any subject you can think of.... from reports about a conference someone just attended to a slide show about someone's vacation.  The "brown-bag" part of the name is an indication that even though the meeting is at lunch time, lunch is not provided and you need to bring your own lunch.  As a weird quirk of American culture, folks who bring their own lunch to work (rather than eating in the cafeteria or elsewhere) often carry it in a brown paper bag, hence the term.

Sorry about the confusion.  In the future, I'll try to explain colloquialisms or not use them at all.