it means you have either added yarn overs or dropped stitches. it might mean you are a beginner or it might mean you are knitting lace and want the holes. or that you are knitting on needles slightly...
Purl is a knitting stitch, which can be paired with normal stitch to make ribbing, stockinette stitch and a few others. Purling is very simple, it is a bit like normal knitting in reverse. To purl,...