AMD or "Advanced Micro Devices" to be exact have been around quite some time now, 1969 to be exact. They are known for CPU's and in recent years GPU's after they acquired ATI back in 2006. As well as Processors and Graphics cards you can also find the AMD badge stuck on RAM and NAND Flash Memory although there is not much focus in this area.
AMD by numbers are 1/10th of the size of Intel employing just under 10,000 people and posting a revenue just short of 4 billion pounds. Whilst being quite a way off their rivals, Intel, they hold way more market share in the custom PC industry than those number would suggest meaning if you are choosing a CPU you are either going to choose AMD or Intel and if you are choosing a graphics card you will be choosing Nvidia or AMD.
We like AMD, they are not afraid to try something new and take community feedback seriously.