im a benchmark guy!
benchmarks are tests that are run using a configuration of hardware to determine how a particular application performs. this is then compared to a bunch of other tests done with different hardware using the same application. this gives people a way of judging the performance of hardware without referencing the specs of the hardware, which can often be misleading especially when trying to compare AMD graphics cards to Nvidia.
you can use any game to benchmark hardware or you can use a specially designed application like 3D Mark. when using a game, if it doesnt include a benchmark as many games these days do, you typically find a run near the beginning of the game that showcases a lot of different effects. you then calculate the average frames per second using another piece of software like MSI afterburner. a program like 3D Mark is an artificial load on your GPU so it wont represent real world performance, but its so ubiquitous that many gamers, like myself, understand the score and judge the performance of the hardware based on that. if you want a free benchmarking tool, the demo for 3D Mark can be found here:
http://store.steampowered.com/app/223850/ just click download demo, run, and in about 5 minutes, youll have a score.