Casting off knitting or binding off is the term used to take a knitting project off the needles to finish it.
Here's how it's done in a few simple steps.
As shown in photos above:
Step 1: Knit the first stitch as usual.
Step 2: Knit the second stitch.
Step 3: Insert the tip of the left hand needle (from left to right) into the first stitch that you just knit on this row.
Step 4: Lift this stitch over the second stitch (this is the stitch closest to the right hand needle tip), and off the needle.
Step 5: Continue to knit a stitch and lift a stitch over and off the needle (as above). until only 1 loop remains. Your bound-off row will start to look like this (see photo above, center)
Step 6: Cut yarn and draw through last loop. Bind off completed!
Knitting Tip: Bind-off loosely! If your bind off is too tight, try going up a needle size or two.