It's defined toward the end of the pattern. It makes a kind of one row bobble.
Knot: K1, p1, k1, p1, k1 into 1 st, then pass 2nd 3rd 4th and 5th sts over first st.
You want to knit into the stitch and then without slipping it off the left needle, prur into the same stitch. Again don't slip off the left needle but continue to knit 1, purl 1 and finally knit one into that same stitch. This increases 4sts. Now you're going to pass the stitches made over the first st so that you're back to one stitch on the right hand needle.
I've made this blanket before and it's a favorite.