Why do preamplifiers have so many capacitors?

I dare say many who buy preamplifiers have no idea how they work internally. It would be wonderful if there was a diagram, a visual guide, allowing someone to understand the internal flow of a preamplifier. Further I never see commentary explaining the flow, and variations, within a preamplifier.

I think many would be grateful with something that illustrates how these mystery boxes work.

Look at a schematic (circuit diagram) to see how parts are connected. 

@jumia-

        IF you are sincerely interested; the first few magazines/books/resources mentioned on the following link, are an excellent place to gain such knowledge.

         They were great to, "grow up" on and: even decades old, they're still fun to bring out and reread.

                          I miss the DIY/hobbyist PAPER rags!

                       http://www.nutshellhifi.com/Linkstxt.html

@jumia-

     Actually: what was supposed to be a link to the following Vacuum Tube Valley site and reprints, wasn’t, on the last reference.

                               You’ll find some good articles, here:

https://web.archive.org/web/20130604042043/http://www.jumpjet.info/Pioneering-Wireless/eMagazines/VTV/vtv.htm

     Be patient, as you're downloading a complete magazine, in pdf form, for each issue.

Watch some of Ron Sutherland videos.