Figuring out the easiest way to use your energy will make you happier and more efficient. It will also better your relationships with others and yourself. Knowing how you operate best makes your days feel easier and your success feel more successful because even though you will be working hard, you won't be working against yourself. Building an understanding of how you work and then how you work in a group will make you a desirable asset because you will end up where you belong and successful when you end up.
I've included some links, diagrams and images so flip through at your own rate and test yourself! At the very end you will find the powerpoint I used during my presentation.
That site is fairly accurate. Sometimes the E/I and P/J are a bit off but as long as you answer as your true self and not your ideal self then you will be fine!