Could I have some help

I found this pattern here:

And it says this:

Body (make 2)
Using US size 3 (3.25 mm) needles and MC yarn, cast on 16 sts.
Row 1: Knit to end.
Row 2: Purl to end.
Row 3: K1, m1, k14, m1, k1. (18 sts)
Row 4: Purl.

What does the M1 mean?

Make 1, it’s an increase and a couple ways of doing it can be found on the Increases page. You lift the strand of yarn between sts with your left needle, knit into it through the back loop so it’s twisted and there’s your new stitch.

Thank you so much! I’ll check it out. I’ve done Increases before but it’s been a while lol