A yarnover is an increase technique made by bringing the working yarn over the right-hand needle before working the next stitch. On the subsequent row, this loop is knitted or purled, creating an intentional eyelet hole used in lace patterns or simply adding a stitch to the row count.
Heard on the job
Make sure you do a full yarnover before the purl stitch so you don't lose the increase.
Insider tip
When a yarnover is followed by a purl stitch, the yarn must be wrapped all the way around the needle to end up in the front again.