yarn.
almost every crochet project begins with a foundation chain. the stitches look like a chain, therefore the name. you will build row upon row of stitches on this foundation chain.
when crocheting in rows, you need to chain a certain number of stitches before starting each new row. these chain stitches are called turning chains. they are necessary to keep the edges of your work even.
when crocheting into a foundation chain, you need to skip a certain number of chains before working your first stitch into the foundation. another way to think of it is making "extra" foundation chains that will serve as the turning chain. for example, if you want 