There is only one way to form a hole in your knitting. This is an easy accident

If you discover the extra wrap immediately, you can rip back to the wrap and place the yarn in the proper position before starting to knit. However, most extra wraps are found on the next row or two. It only becomes an actual stitch if you work into it. At this point, just slide that wrap (or the stitch created by the wrap) off the left needle and work the row normally. That extra yarn will be absorbed by the neighboring stitches.

Creating a hole is the basis of lace when it is done on purpose. This hole is done deliberately in the dish cloth pattern to help the new knitter identify that wrap. Learning what to look for when you do it on purpose, will help you identify it when done accidently. now you know both what causes the hole in your knitting and how to fix it if it is a mistake.
The next lesson goes into more detail on that wrap that we call a yarn over (YO).