Hi there Camille,
Provided that you find Beck's clarification in regards to delimiters satisfactory let's then try and tackle the codepage notion. You might think of them similar to character sets.
Strictly speaking a code page is a table of characters and corresponding numerical representation. This provides the means of mapping the characters to their binary values. Character sets on the other hand are just a collection of symbols without a method of encoding applied.
In simple terms the codepage bit tells Qlik which 'map' to use in order to properly interpret the characters contained in your file.
Please see below an eloquent example:
Unicode is best described at www.unicode.org. The Unicode Standard says "The Unicode Standard is the universal character encoding scheme for written characters and text. It defines a consistent way of encoding multilingual text that enables the exchange of text data internationally..." Basically its kind of a enormous character set that encompasses all of the other characters. It’s encoded in UTF-8, UTF-16 or UTF-32. All 3 UTF encodings are representations of the same set of characters. Windows and .Net (and many other systems) use Unicode natively, and it’s the natural preferred encoding for .Net or Windows applications.
source and further reading here.
I also found this image to be helpful:
Hope this helps!