WHY ARE YOU YELLING?!
WHAT IS THE DIFFERENCE BETWEEN WRITTEN AND ORAL LITERATURE AND MENTION HOW THE TWO LITERARY WORKS HAVE EVOLVED?
DYOH!!!
It's simple ... If you don't understand the difference, you may want to use a dictionary to look up the words "written" and "oral"
Written literature needs no definition. Here's a page from Yale that will explain oral literature. You can easily work it out from there.