Knitting is one of several ways to turn thread or yarn into cloth (compare to weaving, crochet). Unlike woven fabric, knitted fabric consists entirely of horizontal parallel courses of yarn. The courses are joined to each other by interlocking loops in which a short loop of one course of yarn is wrapped over the bight of another course.

Industrially, metal wire is also knitted into a metal fabric for a wide range of uses including the filter material in cafetieres, catalytic converters for cars and many other similar uses. These fabrics are usually manufactured on circular knitting machines which would be recognised by conventional knitters as sock machines.

Knitting can be done either by hand, described below, or by knitting machine. In practice, hand knitting is usually begun (or "cast on") by forming a base series of twisted loops of yarn on a knitting needle. A second knitting needle is then used to reach through each loop (or stitch) in succession in order to snag a bight of yarn and pull a length back through the loop. This forms a new stitch. Work can proceed in the round (circular knitting) or by going back and forth in rows. Knitting can also be done by machines, which use a different mechanical system to produce nearly identical results.