What is a selvage st

i have a ribbed cap pattern, it states…"cast on 106 st. row 1(rs)K1(selvage st.)work in k4 purl4 rib pat. to last st. K1 (selvage st) :??

Well, in sewing, the selvage is the part of the fabric that is inside the garment once you’ve seamed it. So I’m guessing they’re calling your very edge stitch a selvage stitch, because after you do your seaming, it will be inside your hat. Make sense?

yes that makes sense, thank you

Selvedge stitches in knitting are the ones at the very edge of the row.