Help please

I have a new knit pattern I want to try but it has a pattern note that has me stumped .Could someone tell me what the following pattern note means? “Sl all sts purlwise with yarn on WS of fabric”

It means “slip all stitches purlwise with yarn on wrong side of fabric”. So if you are working on the front or public side of the fabric you’d keep the yarn in the back as if you were making a knit stitch, but stick your right needle into the stitch on the left needle as if you were going to purl, but don’t wrap the yarn, just move it to the right needle. That is a slipped stitch and they are common for various stitch patterns and increase/decreases.