Sorry, but I'm another user who is also very confused by this and I don't really understand the subtlety. I've read the sentence "The character set chooses the character set to be used for displaying the actual text ..." ten times but still can't get a picture of it :p
For me and in general, the terms "code page", "character set" and "encoding" are synonyms. Having both things could lead to some meaningless combination. Let's take an example:
In Big5 (by the way, I've no idea why it's called *simple* Chinese, but that's another discussion), Hebrew characters are not represented in it. You could check that by looking up all supported characters in Big5 table:
http://www.khngai.com/chinese/charmap/tblbig.php?page=0
So, if I choose
Code Page: Simple Chinese Big5 & Character Set: Hebrew
This combination is meaningless.
Some other combinations don't quite make sense other, eg
Code Page: Simple Chinese Big5 & Character Set: Shift-JIS
or
Code Page: Simple Chinese Big5 & Character Set: Greek
because Big5 doesn't contain accentuated Greek characters. So, the word "colour" in Greek which is χρώμα (phonetically "chroma") is not possible as the character ώ isn't a member of Big5.
Could I suggest that "Code page" and "Character set" be merged as one option?