Basically, Chr(13) and ChrW(13) are equal.
But ChrW accepts unicode characters, and Chr only ANSI and converts any integer value from 0 to 255 using the current code page to a Char
more information on msdn:
Chr, ChrW Functions
Chr(256) is not allowed, but ChrW(256) is OK (256 is only an example outside range 0-255, I do not know which symbol is behind the unicode char 256)