k2tog is an abbreviation for knit two together. It involves knitting two stitches together as though they were one stitch. Completing a k2tog creates a decrease in your knitting because where once there were two stitches; there is now only one stitch. This decrease slants to the right. If you are decreasing evenly on both sides of your fabric to create a point (such as the top of a mitten) or shaping armholes, you would want to use this on the left side of the front of the garment. On the right side you would use a left slanting decrease such as ssk (slip, slip, knit).
Insert right needle through 2 stitches at once from left to right and complete knit stitch as usual.
Your completed k2tog will look like the stitch pictured here. You won’t be able to see it clearly until you have worked a couple of rows past it. Notice that it slants slightly to the right. k2tog is a right-slanting decrease.