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The bottom right hand corner of the window is its resize control. The green on the upper left resizes the window either to it's last position, or a position that avoids the translucent toolbar known as the dock.
File menu in most applications has a new window command. In those it does, you can have more than one window at a time. The window tile/cascade is one feature not found in Mac applications except by Microsoft and a few others. The yellow control puts the window in the dock, where you can bring it back later. For more, see
http://www.apple.com/findouthow/mac