A high quality filler will be naturally age with time and only time no additives. The very best fillers come directly from Cuba second would be the Domincan republic and so on down the line. There should be no large stems in a high quality cigar.
When the filler is matched and rolled correctly with little to no stems you get a consistant draw with a long burn time from your cigar.
Binder: The binder is made from a heavier larger leaf and is used to wrap the filler to hold the shape of the cigar.