Hi Clive - Responsive behavior is about the entire interface changing and reconfiguring itself to support smaller screen for factors and devices. I have prepared a number of screen shots for you to see the difference.
Note that it is much more than just resizing and window and an object.
Stand by for screen shots.
These are live shots of my devices (using AirServer - for the iPad and iPhone) - the entire interface will reconfigure and resize per device and size to accommodate different form factors. The concept is know as "Responsive Design" and it is an approach design to provide the most optimal viewing experiencing no matter what size or device is being used. Navigation, gestures, menus, objects are all reconfigured to allow interaction.
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Good answer Michael. Another resource that you may find useful is this 'A List Apart' article from 2010:
Its author, Ethan Marcotte, was the first person to coin the phrase 'Responsive web design'.