Crochet quilts, potholders, and mittens would just be endless jumbles of webs without the appropriate edges to finish them off and give them polish. There are many different ways you can create edges in crocheting, but the crochet foundation chain is among the more creative.
This is the left handed version on crocheting a foundation chain. Foundation chains are more complex but allow for better edging possibilities. Mikey recommends using Foundation Chains as much as possible, especially when doing edging.