Closing files:

In order to close the files you have open, you have multiple options at hand. Remember that if you have any unsaved data in a file, Notepad++ will always ask you if you'd like to save those changes before closing any file.
Primarily, you can close any file by selecting File->Close or press . To close all files, select File->Close All or press . To close all the files but the active one, select File->Close All but Active.
You can also close any tab by clicking on it with the middle mouse button. This way you can close tabs without having to bring them to the foreground.
There is also a setting that allows you to close any tab by doubleclicking on it, or show a close button on each tab(). To see how to do this, see the section about configuring the Tab Bar in the Preferences dialog (see Preferences).
Finally, you can close any active tab by clicking on the cross in the top-right corner of the menu bar.