These are four basic granny squares. Ahh, the lowly granny square. But NO! The squares are very versatile! There are soooo many possible color combinations and, yes, even pattern variations.
The basic granny square is actually worked in "rounds," and not rows. It is very easy to make. The "how-to" links at the top of the page will direct you to instructions on how to make one. The basic square uses double crochet and chain stitches, with a couple of slip stitches to join the rounds.