The word "satisfied" is a more basic word that describes the meeting of needs, satiation, whereas "fulfilled" describes a loftier feeling of pleasure after having accomplished a meaningful goal or fully developed one's natural gifts.

For the most part you can use them interchangeably. The only difference is that I would tend to use "fulfilled" for more meaningful subjects. For example, "He is fulfilled now that he is married" or "Nothing fulfills me more than having my family around." I tend to use "satisfied" for less meaningful things such as, "that spaghetti was satisfying." It can be used like the word content - such as, "are you satisfied?" In terms of completing an agreement/contract they are both the same. "He fulfilled the contract." "He satisfied the requirements of the agreement." I hope that helps!

They are not even interchangeable. Come on. Try a dictionary. www.thefreedictionary.com