Deco squares are used for, well, decoration... you can use them in many different ways... as photo anchors, page anchors, on top of a strip of cardstock to make a topper or border, on top of ribbon or fiber to make a deco element, etc. I've seen them as small as 1 inch and as large as 2. Many here use the CM punches, which is 1 1/4 and 1 1/2 matted. Larger ones give you a little more flexibility in design if you want something intricate.