When knitting two stitches together depending on how they're knitted they'll point towards the right or the left. Usually, when we're knitting on the right side of the work we'll want the decrease to point to the left, for that we knit the stitches on the back loop. The same way, when we're knitting on the left side of the work we'll want the decrease stitch to point to the right, for that we take the stitches together through the bottom of the front loop, and the second stitch on the left needle before the first, as shows in the diagram.