Well, Dave, the thread title is a bit awkward and would have been better titled "Folk Mass Music," but we generally leave threads with the title they were started with unless the title is totally unclear. They're talking about folk-style songs written or used for liturgy. Very little of it was what most of us would call "folk," but most of the songs had three chords or fewer. Some of it was corny, but it made Mass fun for a change. It was mostly written for Catholics (Sydney Carter fans might disagree), but many denominations used it.
-Joe-