The difference between Supersampling and Multisampling

(link) “Supersampling” is an antialiasing technique that is simply a brute-force approach. A graphics processor that uses supersampling renders the screen image at a much higher resolution than the current display mode, and then scales and filters the image to the final resolution before it is sent to the display.
(..) Multisampling requires a more sophisticated GPU, however, so only the newest GPUs available support this technique. The basic idea behind multisampling is to embed the intelligence behind antialiasing inside the core of the GPU, in hardware.
(..) You can think of these extra samples as extra “virtual pixels. The GeForce3 GPU has wider data paths internally so it can handle these extra virtual pixels without slowing down its standard rendering speed. In fact, the GeForce3 GPU can compute these “virtual pixels” or additional samples at full speed, with no reduction in engine performance whatsoever. These wider data paths enable GeForce3 to use the same texture data for all of the samples in the pixel and significantly reduce the memory bandwidth required to texture all of the AA samples.