Asterisk (*) and question mark (?) are wildcard characters. The asterisk matches any sequence of characters, whereas the question mark matches any single character. File masks contain wildcard characters (e.g. *.a? matches .a1, anything.ai, etc.) and are separated by semi-colon (e.g. *.txt;*.doc matches a.txt, b.doc, etc.). Excluded masks are placed after vertical line character (e.g. |*.txt;*.doc matches anything except *.txt;*.doc). If you need a semi-colon inside mask, type it twice (e.g. one;;mask).