Hi, I don’t know if it has a name, but you do just what it says. I know the first time you hear some of these things it seems impossible to do what they say, but if you do them step by step they actually do work.
First purl the next two stitches together. If you have never done that, you just have the yarn in front so you can purl, then run the right hand needle into the first stitch on the left hand needle purl wise and then on through the second stitch in the same way. Then purl them together as one stitch, but don’t slide them off the needle yet. Now bring the right needle tip back into position to purl again and purl into the stitch closest to the tip of the needle again. Now let both of the stitches that you have worked into slide off the left hand needle.
It’s kind of a decrease (p2tog) and an increase (p back into the first one again) at the same time. You end up with 2 stitches where you had 2 to start with (stitch count remains the same), but it makes a little different look and they want that for some reason.
I hope that helps.