This pattern uses US Crochet Terms & Stitches
ch(s) - chain(s)
sp(s) - space(s)
st(s) - stitch(es)
rnd(s) - round(s)
sc - single crochet
beginning inv. join - beginning invisible join + color change
inv. join - invisible join + color change
finishing inv. join - invisible join done on the final round of your square
SCC - single crochet corner = work (sc, ch1, sc) into the back loop of the ch1 corner sp
ddc - dropped double crochet - a regular dc (double crochet) made into the unworked front loop of the stitch two rows below your current row.

Yarn Needed for ONE granny square-
in Aran (worsted, 10 ply, #4 weight)
Finished Size is about 8.5 inches (21.5 cm)
5mm Hook
50 yards (46 m) for each color - 2 colors per square - Color A (the design) & Color B (the background)