Remember the "Calvin and Hobbes" strip where Calvin shows Hobbes how a toaster works? After the toast pops up, they both wonder where the bread went.
Aristotle could have told them the bread was the material cause of the toast, and through the efficient cause of the toaster, which effected the formal cause of toast, ceased to be bread and became toast, with the final cause of... well, maybe to be eaten, or perhaps to be used to build a fort on the living room floor. With Calvin, the final cause isn't always straightforward.
In short, the material cause of a thing is what it is made out of; the formal cause of a thing is what it is to be that thing (i.e., its form); the efficient cause of a thing is what produces that thing; and the final cause of a thing is what it is for.