It's done in short rows, where you don't knit all the way across, but turn and knit back, leaving stitches at the end of the needle. It shapes sock/slipper heels and to add to a sweater for a large bust. You wrap the stitch that's being wrapped, then knit the wrap with the st later when you come back to it again to prevent small holes. Here's an article
that may help you understand it.