If you read the first page of each swap, it will describe what that swap is all about.
Some are for blocks, squares (like the I spy fabrics) FQ's, bricks, strips of fabric.
Some of the swaps are really round robins. You make the center of your quilt, then everyone starts sending them to other's according to a list. The other's and you, add on a predetermined border and then send it on to the next person. When you get your's back, the top is complete.