I've been using Ms Word 2013 for a while, and suddenly in one of my documents, this has appeared..(See pic below)
note- If I create a new document it's not in the new one
Added
I don't yet know how it went into that mode.
It has been pointed out in comment that I can click that "tab" where it says header and footer tools, and then I can click "close".
Then though what happens is the image I have in my document gets greyed out and I see no cursor. Then when I double click in the document, I get the cursor and the image is no longer greyed out but I am in that header footer mode again.
Here is an example, see header and footer mode is closed but the image is greyed out and the cursor if it's even there, isn't going within or before the text above the circle picture, even when I click in that text.
I notice now that the cursor is actually going to the bottom of the page
pic still greyed out
It's as if maybe somehow the text and pictures are stuck in a giant header that is taking up the whole of the first page and can't easily be edited at the same time as the rest of the document can.
I never normally mess with headers/footers at all.