How do you capture video feed from an xbox?

I want to start capturing video and audio feed off of my xbox 360 to make videos to put on you tube but i was told i need things like a capture card to do so. can somebody tell me everything i'll need to do it and how to do it. and if it's possible can i use it to pick up the audio feed of a xbox live party. and can you try and make the explanation as simple as possible im not that smart.