Crochet is always done with one hook, knitting requires two needles.

This is a terrific learning website:
http://crochetcabana.com/tutorials/index.htm

Scroll down to basic stitches, single crochet and double crochet are really all you need to know at first. Further down is a granny square pattern those are great to learn on and use up scrap yarn. In fact this site has a ton of info on granny squares and lots of tips and trips.

Have fun!

EDIT: The responder above is correct, there are many sizes and types of hooks to choose from. Once you learn the basic stitches and what gauge means you will no doubt want more hooks. The smaller the hook, the tighter the stitch and lighter weight yarn used, larger hook bigger stitch for heavier weight yarns.
But you still only need one at a time.