When I first started to crochet I learned, without a pattern, to make slippers. This was my first lesson in tension as well as gauge. Needless to say, one slipper could fit my 6 year old and the other my 3 year old. How tightly you crochet (tension) determines the gauge of your work. When you read a yarn label there is a small diagram that will tell you how many stitches and rows you will need to get the appropriate gauge. Going from there you can either increase or decrease your hook size to make your square match what is says on the label. This is called your gauge.