I just refer to is as a background, Patti - but you could call it a background montage too.
And that particular capture:
comes from Ep #266, which originally aired on July 3, 1967. At that particular point in the story Liz[spoiler]went to Widows' Hill a few times to contemplate jumping off rather than marry Jason - and in that particular instance of the capture Mrs. Johnson discovered Liz there and the two discussed the widows and how legend said they were awaiting a fourth women to join them.[/spoiler]