Interestingly, before they added the iOS-style fullscreen mode, the "maximise" button on Mac OS X would actually just fit the window to the content, rather than the screen.

A common frustration to those used to Windows or Linux, while the Mac folks were equally confused about why people wanted full-width windows with miles of empty space on either side.

Just whatever other software I'm using. Usually terminal windows, sometimes text or graphics editor, e-mail client. That kind of thing.