Yarn back

I am working on a child’s sweater and the directions call for “slip first stitch as if to Purl, yarn back” Can someone tell me what that means?? thanks!

When you slip “as if to purl”, you have your yarn at the front like you would if you were purling except that you will just move the stitch from the left needle to the right without actually purling it. Now, when it says “yarn back”, all it means is to return the yarn to the back of your work by bringing it in between the needles to the back.