This started in 1972 (a few years before I was born), and it's still going strong. Unfortunately, I have seen very little of it, and usually I'm not even aware that it's on. (And when I am aware, I usually either have something else to be watching, or else just can't motivate myself to bother watching it.) Which I feel bad about, because I'm sure I'm missing a lot of great stuff. Different installments present different things like plays, films, dance, concerts... anything that falls under the general category of "performing arts." And I guess that's all there is to say, other than to list the few installments I have seen.
And, um... looking at TV.com's episode guide, the only ones I'm sure I've seen are Peter & the Wolf and The Hollow Crown, though I feel like I must have seen more than that. But then again, I'm often wrong about things I'm sure of, so maybe I haven't seen anything else except bits and pieces while channel surfing. Of course it's also possible that TV.com's episode list is incomplete, and just happens to be missing something I've seen. There are also some things I may have seen on another PBS anthology series of which I've watched shamefully few installments, "American Playhouse."