They are strictly for use with other characters. They are used for example in French to produce letters like é and è.
No, they are diacritical marks as for French, Spanish, etc. My keyboard isn't set up like that. (It's set up for English only, and thus, unless I'm using a foreign word, I don't need the diacritical marks, and when I do, MS Word supplies them for me automatically.) The reason they looked different is because they were 'smart quotes' that MS Word automatically does. They only appear here if I cut and paste - like this: ‘smart quotes’.
Well, it sounds like from what you are saying, Terry, that they are called single quotes. I couldn't remember what they were called, but now that you say that, it's jogging my memory.
And I had no idea that speech was ever encased in the single quotes. I don't think I've ever seen that. (Mental thought and your example of a quote within a quote, yes, but not for speech like: Clark said, 'Yes.' All I've ever seen is: Clark said, "Yes." Hmmm... Very interesting.)
Thanks, guys.