http://www.knittinghelp.com/knitting/basic...niques/misc.php
Ribbing is basically a combo of knitted and purl stitches. The purl stitches create the valley of the rib and knit stitches create the raised part of the rib. You can really do any combo of them depending on how stretchy you want you ribbing and how big. I made a baby hat with a 2 knit 2 purl pattern