How to "Include in next Stitch?"

I’m not sure what it means to “include in next stitch?” Does this mean increase by a yo or M1? In my pattern it reads - Cast on 14 Stitches. Row Two: K1, inc in next st and repeat to end - should end with 21 stitches. But I always end with way more! Any insight would be great!

Thanks!

Inc doesn’t mean ‘include’, it means ‘increase’. So you would increase by knitting into the front loop, then into the back loop of the next stitch. A yo leaves a hole as well as putting the inc between two sts, which is what a M1 does too. To get the sts to come out right, you need to kfb which uses a st to inc 1 instead of putting it between sts.