What exactly do you use a cast iron for....

I just sauteed some sliced potatoes in olive oil/butter mix, with a little rosemary and Emerils seasoning in my new cast iron pan. Half of it is stuck to the bottom and burnt!
i thought the whole concept of cast iron skillet was the browned bits in the bottom gave flavor to the whole dish. Granted this is my first time using a cast iron so maybe i don't know what i can and cannot cook on the skillet......
Help!