Weft knitting is the earliest form of knitting, made using a single element, or one continuous yarn. A set amount of stitches are set up or 'cast on' as the first row. Working from right to left, each stitch is 'picked up' on the left by the right needle, interlocking a new loop/stitch through, and passing it to the right needle and so on. Weft knitting is worked in horizontal rows (think weft goes left) which unlike weaving can be quickly unravelled.
Stocking/Plain stitch (diagram) is the most common form of knitted stitch used and it was first discovered in artefacts from as early as the 11th Century, not to be confused with similar looking textile techniques like crochet, nalbinding and sprang. Many other knitting stitches can be used in weft knitting such as Purl, and Double Knitting. Various combinations of these stitches paired with any number of yarn weights and colours are used to form a vast array of knitting patterns such as such as Cable, Fair Isle and Aran to name but a few.
Weft knitting has since been adapted to be made on machines whereby the construction is essentially the same albeit a little more complex but is a much faster process. While it was invented to speed up the manufacturing process, it also allowed for patterns to be made more uniform for mass production, and also meant that less mistakes were made as machines are designed to prevent dropped stitches causing ladders. Nowadays many of the knitted garments that are mass produced are produced in factories using knitting machines. Weft knitting by hand or machine can be constructed flat or in the round.
Types of Weft knitting include Jersey, Double Knit, Circular Knitting, Fair Isle and Cable knit. All of these knits are generally produced using a knitting machine as a finer gauge, more delicate fabric can be produced but hand knitting is still used, mainly as a hobby due to the investment of time needed.