Stockinette Stitch is the fabric created when you knit on the RS and purl on the WS.
It is the basis of most knitted garments. It tends to curl in on itself when it doesn’t have a border that lies flat.
Stockinette Stitch (Flat)
Row 1 (RS): K.
Row 2 and all WS rows: P.
Stockinette Stitch in the Round
All rounds: K.