K2tog is a simple decrease, meaning you remove 1 stitch from your stitches count on your needles. It leans toward the right.
It consists to knit together 2 stitches.
Work according to pattern until you need to make a K2tog decrease.
Pass the tip of the right needle into the 2 first stitches from the left needle, going from left to right.
Pass the working yarn arount the tip of the right needle and pull the new stitche from the 2 stitches.