tarabyrne04 - They don't reallyy curl your hair in the sense that hair rollers do. But, you can - VERY CAREFULLY - wrap your hair around one of the ceramic plates, and then press the plates together briefly. Remember - hair straighteners should never be on any one piece of hair for longer than a split second as it will seriously burn.
Not too sure I agree with whoever said that you could use hair spray instead of straightening iron spray, although I do agree that having a specially dedicated spray is a bit of a con to make more money out of us. In my experience, as long as you used enough leave-in conditioner and straightening balm, your hair will be fine.
If anyone is in a dilema about buying ceramic straightners, watch out for the cheap imitations that use "ceramic coated" plates - it's not the same! Also beware of products that have orange plates - ceramic should be more of a yellow colour. I wanted a good brand but couldn't afford it, so bought a brand new Hair Tools one from ebay for a 1/4 of the retail price.