AMD was known as the primary competitor to Intel in the traditional CPU market, 5 years ago AMD acquired ATI, the 2nd graphics card maker on the market (to NVIDIA). Once AMD acquired ATI they began developing CPU+GPU combo chips targeting laptops specifically because they saw the market shifting from a desktop environment to a mobile environment. Around that same time NVIDIA began investing into mobile processors because they saw the market shifting as well.
As these two major processor companies began shifting their core development principals, the marketplace began to shift as well. NVIDIA began to slip a little in the GPU department, and gain in the mobile market. AMD began to slip in the desktop processor market but gain in the laptop and GPU market.
Now we begin to see a completely different landscape in processors. NVIDIA is seen as a leader in the mobile processor market with it's Tegra lineup, powering such flagship devices as the Verizon Motorola XOOM tablet (the first Android 3.0 Honeycomb tablet on the market), and the At&t Motorola Atrix (the first available dual-core Android Smartphone). AMD is now a leader in the laptop processor market and the laptop GPU market. The latest step for AMD was being selected as the GPU in the newly announce MacBook Pro computers. MacBook Pro's have been the laptop and computer of choice for some time now of graphic designers and developers, who are in demand of the highest performing graphic processors. Three years ago NVIDIA would have been an easy choice for the GPU in the MacBook Pro's but now AMD is the choice, not only because their processors consume low amount of power but because their performance is through the roof.
In an ever changing marketplace of processors and devices, these two companies are shifting their core focus in different directions and it's hard to tell which ones long term strategy will pay off, but where we are right now AMD has taken a strong stance in the graphic marketplace and NVIDIA has taken a strong stance in the mobile marketplace. It will be interesting to see how this is all going to play out.