This stitch creates one stitch from nothing - it's also sometimes known as a lifted bar increase and is not to be confused with the kfb style increase, which uses a stitch whilst creating one

1

With the tip of your right-hand needle, find the bar which runs between the stitch you've just worked and the stitch you're about to work. Insert the tip of your right-hand needle into this bar from front to back, lifting it up.

2

Place the bar onto the tip of the left-hand needle and then take away the right-hand needle.

3

Now insert the tip of your right-hand needle into the BACK of the bar you've just lifted onto the left-hand needle. Wrap your yarn around the tip of your right-hand needle, the same as you would do for a knit stitch.

4

Finally, pull the bar off of the left-hand needle. You have completed the "make one" stitch, increasing your stitch count by one.