What is a Pineapple Stitch?

I was looking for instructions on doing a border on my large rag rug I'm trying to complete and came across this site. I'll have to add it to my favorites. As a matter of fact, I make my rugs just like Grandma made hers. My only problem is, what is a pineapple stitch? I sure hope I can get some answers from the experts on this site.