Thank you all. "When I was a boy.......", if I recall correctly, we had electrolytic, ceramic and paper. Today there is mylar, tantalum, polyester, mini electrolytics, and whatever else I do not know. It was simple, electrolytics in PSUs, ceramics in coupling and bypass, and paper for oscillator ckts.
Now it seems that the use of capacitors ( a very simple concept) has become extremely sophisticated. I have followed (tried?) some of the threads regarding "esoteric" (to me) uses and now I am ready to continue my basic studies with the next topic being capacitors. It now has tremendous relevance. Much more to the topic than time constants!
This looks to me like it can be a more complicated subject than transistors! I love it.