The CPU and memory work together to run programs.
Most computers have a CPU and a separate graphics processing unit (GPU) for images. The GPU can be around 10 times faster than the CPU. It is optimised to produce high-quality 3D graphics for games and films. The GPU is responsible for handling images and frees up the CPU to do all other tasks.
CPU, memory and bus speeds will all affect the overall speed of a computer. If one is significantly slower, then it will slow down the others.
Benchmarking is a test used to assess the performance of a computer. Different types of benchmark software are used for the different kinds of application you might want a computer to do.
It is difficult to assess the performance of a CPU because a computer might excel at some tasks but not do so well at others. For example, a computer that is going to be used for gaming will require the best combination of hardware to handle intensive graphics quickly. The same computer might not perform so well if it was used to analyse vast amounts of scientific data.