Eyelet stitches in knitting will make little holes that add interest to a knitted item.
It’s very easy to do this:
In the round, when stitches are even, or 2×2, this will work, because 2 stitches are used. Or space out the holes as needed.
YO, k2tog (Yarn over, knit 2 together)- this makes the hole – simply knit the next row or rows.
Other stitches can go between the eyelet stitch, for instance: k4, (YO, K2tog), K4, ….
Below is a photo of the cowl I am knitting. It is not a pattern and I am making it up as I go. I am adding eyelet stitches in some of the rows to add texture.
See this post and video for a Staggered Eyelet look.