A very easy way to transfer a design to the fabric of your choice. Just put the A4 sheet into your printer, press print and out she comes. Just peel off the backing and stick to your fabric.
You can stitch through both layers, then when finished, just rinse away the stabliser. Easy!
I wouldn't recommend this for "heirloom" projects as you don't really want any sort of glue near something very precious. But great for quick and easy projects with not too many very small stitches as you do have to stitch through 2 layers.