Literature = Letters?

Most of the people, think that literature are books, letters, and the people who wrote them.

If you write "literature" in google, and search for images, they are only books and that kind of things.

 Literature is also everything that surrounds a text, the social-cultural context, the time, almost everything!

The study of literature is very controversial during the time, specially when we need to study the best form to analyzes texts, or we need to know what things I need to have in mind when we analyze a literature piece. And always appears this question, when literature appears?