Slip Stitch
A slip stitch is moved from the left to the right needle without being knitted, used in edges, decrease combinations, and mosaic knitting.
Explanation
A slip stitch is passed from the left to the right needle without being worked through. It can be slipped either as if to knit (twisting it) or as if to purl (not twisting it), depending on what the pattern calls for, and this affects how the stitch sits afterward. Slip stitches are used in edge techniques for a neater border, in decrease combinations like 'sl1, k1, psso', and form the very basis of mosaic knitting, where stitches are slipped in a contrasting color to build up a pattern.