I remember when our family computer first got a 3D accelerator card. My brother had stuck a post-it on the display, instructing me to load up my user account and check the wallpaper: he had made one in MSPaint, which read in big, black letters: "we have 3Dfx!" You know, one of those that you had to connect to the VGA port - it was not a video card, but a graphics accelerator card. Later on, video cards and graphics accelerators became one.
On laptops, you generally cannot upgrade the video card. You're stuck with whatever chipset you bought - leaving you with a tough choice: do I go for portability, with a less powerful chip to ensure better battery life, or do I go for the powerful chip and sacrifice battery life? AMD came up with a solution, one that I personally find rather appealing. It's called the eXternal Graphics Platform (XGP) and it's a separate box that you connect to your laptop whenever you need additional graphical power. Fujitsu-Siemens had had a demo implementation of the XGP.
They are designed to be hot-pluggable, and they do not require an external display. The obvious problem is that they require a special XGP connector (a remodelled PCIe 2.0 connector), which, of course, isn't implemented yet on any laptop. The concept is interesting, but the success of XGP will depend solely on the amount of effort AMD puts into pushing it.