Most people are familiar with the giga hertz (billions of instructions per second) measure to describe how fast a single CPU's processor is running. Most microcomputers of today are running around 3 GHz or 3 billion instructions a second. Although 3 billion sounds fast, many of these instructions are simple operations.
Supercomputing uses a measurement involving floating point arithmetic calculations as the benchmark for comparing computer power. "In computing, FLOPS (or flops or flop/s) is an acronym meaning FLoating point Operations Per Second." and again "On May 25, 2008, an American military supercomputer built by IBM, named 'Roadrunner', reached the computing milestone of one petafop by processing more than 1.026 quadrillion calculations per second." (FLOPS from Wikipedia) For those of us not familiar:
Example 24.5: Getting a Sense of Power
3 billion or 3 GHz is: 3,000,000,000 l quadrillion or l pedaflop is: l,000,000,000,000,000
You also should realize that your personal computer is not doing 3 gigafolp worth of calculations, but something slower when using the FLOPS measurement.