How did feudalism come in to being?

Write a single spaced, MLA format, NO PLAGIARISM, 2-3 page essay describing the rise of Feudalism and its function in Medieval Europe. Try to give as many details as possible please, but the main questions that absolutely HAVE to be answered in full detail are: 1.)How did feudalism come in to being? 2.) How did it work? 3.)What was the need for it? 4.) Why did it decline?