A GPU is almost like a separate computer inside your computer suited to one specific task. It's like having a gaming console attached to your motherboard. A CPU can more or less do anything. After all an "integrated GPU" is really just the CPU doing the job of the graphics card as well as its own. The problem is that for most types of use for a PC, you don't need a GPU at all. Office computers, casual users just browsing the web and watching movies, store computers etc don't really need a GPU, because their tasks do not require lots of processing power. Conversely there's some tasks/activities, like gaming, rendering, cad/cam software and others that do require a lot of processing power, a disproportionate amount compared to most other things. So the solution is to have a "separate" computer inside your computer, with its own processors and its own memory, dedicated to those tasks specifically and since software is written around this industry convention, the GPU will perform those tasks more efficiently. Something like a server, used for different tasks, won't have a GPU at all, but it will have multiple CPUs and tons of storage space because that's the kind of resources it needs for its tasks.