Rib stitch (2x2)
Rib stitch forms a stretchy, elastic but fitted form of fabric. It is often used for cuff and collars of garments. It forms a nice looking fabric, almost like corduroy, with a texture of vertical stripes.
1x1 rib stitch is probably the most common form. But there are loads of variations, like 2x2 or 3x1. Some rib stitches are more elastic than others. As a rule of thumb, the wider the ribbing, the less the elasticity.
Abbreviations: k = knit; p = purl; st = stitch
Instructions (when your number of stitches can be divided by 4):
Row 1: k2, p2 to end
Repeat row 1 for pattern.
Instructions (when your number of stitches can be divided by 4 plus 2 extra stitches):
Row 1: *k2, p2, rep from * to last 2 st, k2
Row 2: *p2, k2, rep from * to last 2 st, p2