narrow character vs wide charact

char is used for so called ANSI family of functions (typically function name ends with A), or more commonly known as using ASCII character set.

wchar_t is used for new so called Unicode (or Wide) family of functions (typically function name ends with W), which use UTF-16 character set. It is very similar to UCS-2, but not quite it. If character requires more than 2 bytes, it will be converted into 2 composite codepoints, and this can be very confusing.