What is "casting on" in knitting?

"Casting on" is the term for securing the first row of stitches onto the knitting needle. The first step in casting on is to tie the yarn to the knitting needle, usually with a slip knot.

There are numerous techniques for casting on. The most basic method is the knit cast-on: a new loop is pulled through each previous loop and added to the row of stitches on the knitting needle. Other common methods are the cable cast-on, the single cast-on, the double cast-on and the provisional cast-on. The Turkish cast-on is used for circular knitting. After casting on, begin knitting the next row of stitches by inserting the right needle into the first stitch on the left needle.