Wow, CMS a huge topic. I suggest you re-post this question
here[
^] it isn't really a suitable topic for Q&A IMO (which is more desinged for simple question/answer rather than discussion) .
Where to learn the concepts depends upon the technology you are going to use. For example, the sites specializing in Windows Workflow are going to be confusing if you are going to use a Java workflow engine. The same goes for CMS, though you could try Wikipedia for both these terms and you'll get generic basic information, as well as links to helpful sites.
[Edit] Fixed some "Eccentric" usage of the English Tongue!