The most typical 9 square quilt is queen size. This means that it is 6 blocks wide and 8 blocks long.
Each block is made up of nine squares of contrasting fabric - these squares are cut at 4x4inches. (So they will be 3.5x3.5 when sewn - meaning that the block made out of them will be 10.5 inches square.)
You can create many different designs using the 9 square method - it depends on colors and placement. You can make a scrap quilt that includes all kinds of fabric - these are my personal favorite. You can also use 2 colors throughout an entire quilt. Or you can stray away from patterned blocks altogether and create 8-bit characters, landscapes, and words.
Above are some examples of different quilt blocks.