Circular needles are used for projects that you would want to knit a circle, like a hat. But, you can also knit back and forth on them, that's what I do, to make flat projects, like a scarf.
What I did when I was ready to follow a pattern, is found a abbreviation key. Once you figure out what each abbr. means, you're pretty much ready to go. You don't have to learn them all, but the basics.
I think
www.knitty.com has a key in their pattern section. Good luck!