Did you check
Number Formatting documentation? I think it might help you.
The
c is for currency and depends on the culture (your language and country).
The
0.000 is the format where 0 is space for a digit while "." might be decimals separator or the group separator.
I.e:
If your culture is en-EN and you are displaying 1.234, your number will be one unit and two hundred thirty four thousands of unit BUT if your culture is de-DE, you are representing one thousand two hundred and thirty four units and the number is displayer with 3 decimals.
The first 0 is, afaik, the argument number (always 0).