Either Joe O. or somebody else was talking about the difference between Gershwin or Cole Porter songs and folk songs, both of which may be familiar to many people. If I may try to nutshell what I think he was saying, "standards" are sung by someone to an audience; folk songs are adopted by a wide group (perhaps in accordance with the intention of the author). The one Gershwin song I'd call a folk song is "Summertime"--but then Porgy and Bess was called a folk opera.

So "folk" can mean any of three kinds of songs to me. 1) Anonymous and probably the work of many voices through the "folk process". 2)Composed with a strong influence of the styles of music of type 1. 3) Performed by people with or at least for each other.

The first week I was in college, I remember fellow freshman gathered around the piano (played by a sophomore) and singing Beatles songs, "Those Were the Days", etc. If I could sing I would have joined them. (It doesn't take a psychologist to figure out why new college students might enjoy a combination of togetherness and nostalgia.) There's a big historical and musical difference between "Ticket to Ride" and "The Water is Wide", but the social difference may not be that great.