When you open a document or folder in OS X, the top of the window will include the file or folder name and a small icon showing the type of item being represented by the window. Besides informing you of what documents the window corresponds with, this little detail is exceptionally useful for performing a few different tasks pertaining to the represented item.
Viewing the full path
If you need to see exactly where the file is located on the hard drive, you can right-click or Control-click the title, or press the Command key while clicking the title. The resulting menu should show the file path of the document, and you can select any of the folders to open it in the Finder.
You can also do this for any Finder folder to move up to one of the parent levels in the folder path. Keep in mind that if you right-click or Control-click the title, the current window will display the selected parent folder; however, if you Command-click the title of a Finder window, you will open the selected parent folder in a new window.
Drag files and folders
In addition to interacting with the file path for a file or folder, you can use the window name to move or copy the current file or folder represented by the window. To do this, just click and drag the title by its icon to the desired location. If the window is a Finder folder then it will be moved to the new location, but if it is an open document then an alias will be created if the destination is a Finder window. This can be changed so the document is copied to the destination by holding the Command key during the move.
If you use this method to drag the file to another opened document, then, if allowed, it will be copied to the document in a way supported by the application that is handling that document. This is useful for dropping an opened document into an e-mail you are composing, or for placing opened pictures and other media into a document layout you are working on in Pages.
Keep in mind that for this to work, the current version of the document must be saved to disk. Therefore, if you have created a new document in an application, or modified an existing document, the icon at the top of the window will either be nonexistent or dimmed and you will not be able to drag it.