Document displayed at the top of the Finder window
I suspect you are dropping documents on the Finder toolbar without realizing it. 

A document, a folder, an application, any item can be dropped on the toolbar to act as a shortcut, a navigation aid, an alias to a Finder view. Perfect place for a Trash button. Hold down Control and click on the toolbar to see choices about what appears, as well as Customize Toolbar.

To remove an item from the toolbar, press Command while dragging it off. Poof. 

Or should I say, Boom.