<benchmark> A standard program or set of programs which can be run on different computers to give an inaccurate measure of their performance.
"In the computer industry, there are three kinds of lies: lies, damn lies, and benchmarks."
A benchmark may attempt to indicate the overall power of a system by including a "typical" mixture of programs or it may attempt to measure more specific aspects of performance, like graphics, I/O or computation (integer or floating-point). Others measure specific tasks like rendering polygons, reading and writing files or performing operations on matrices. The most useful kind of benchmark is one which is tailored to a user's own typical tasks. While no one benchmark can fully characterise overall system performance, the results of a variety of realistic benchmarks can give valuable insight into expected real performance.
Benchmarks should be carefully interpreted, you should know exactly which benchmark was run (name, version); exactly what configuration was it run on (CPU, memory, compiler options, single user/multi-user, peripherals, network); how does the benchmark relate to your workload?