Stupid question?

I'm knitting these cute little baby sweaters from Simple Knits for Cherished Babies. It's the Chunky Knit Cardigan. I'm working on the right front. It says to purl 2 stitches together through the back loop. I've never seen this, and I'm not sure how to do it. I went to www.knittinghelp.com which is always so helpful for me, but I just couldn't figure this one out. Anyone know how to help me with it?

Thanks a ton!!