Loops are segments of yarn bent into an upside-down "n" shape. The process of knitting is the process of creating and manipulating loops. Knitting machines hold and manipulate loops with needles; needles which are currently held on needles are called active loops.

Machine knitting operations can be described in terms of their action on loops: tuck adds a loop to a needle; knit pulls a loop through the existing loop(s) on a needle, dropping these loops in the process; split pulls a loop through the exsting loop(s) on a needle, moving these loops to another needle in the process; amiss does tugs on the loops on a needle; drop drops the loops on a needle; and xfer moves the loops on a needle to another needle.