Crocheting in rows & the half double crochet stitch

Crochet 4 sc into this foundation chain. Where you put your hook for this first row after a foundation is a little different from how you crochet in rounds. You'll also need to learn how to half double crochet stitch (hdc) for this row. Don't know what any of that means? Watch the whole Row 2 come together below:

You just crocheted in a straight line (woo!), which is called "crocheting in rows." Here's what you just did:

Row 1: ch 21  (21)
Row 2: sc in the second ch from the hook, 4 sc, 10 hdc, 5 sc  (20)