Pattern Help

I am trying to knit a toddler vest and do not understand the instructions. Can anyone direct me to a video or tell me what this stitch configuration is called so that I can google it.

My pattern reads: insert needle under next horizontal loop of row below (between sts) and knit this st.

The vest looks really cute. The pattern is called Toddler Girl’s Vest by Suzetta on

Thanks in advance for any help

That’s a make 1 (M1) increase. Check the increases videos page.