P2, yb, sl1, k1 help

I have a patternice which says p2 yb s1 k1 psso k3 k2tog I’m struggling with the p2 yb s1 part as after the slip I need to k1 so my yarn will be at the back so not sure what the yb means or how it helps my pattern … please help !!

Welcome!
Yb is yarn back. After the purl 2 the yarn is in front. Bring it to the back over the right needle which will make a yarn over and create a stitch. Next, slip 1, knit 1 and pass slipped stitch over the k1.
You’ll have to make sure that you’re passing the slipped stitch over and not the yarn over.

What’s your pattern? Can you link to it, or what’s its name and who designed it? Are you supposed to be increasing as you make the decrease?