How do I knit throught the back loop?

I am trying to tighten up my knit/purl stitch and someone said to knit through the back loop on the last stitch. Does that mean knit as usual and also knit through the back, or just knit through the back? Thanks. :shrug:

Just knit through the back. If you do both you would end up with an extra stitch, and we don’t want that!

My visual is that when you normally knit. you are going into the stitch from left to right, through the back loop or tbl you go into the stitch from right to left on the back of the needle with working stitches.
:shrug: hope that offers additional help