What is a GPU? Why do we need one? Should a beginner buy a GPU?

[vaibhawvipul]

Is your feature request related to a problem? Please describe.
A lot of people ask and are confused why GPUs are needed.

Describe the solution you'd like
A clear and concise description for the beginners explaining how to GPUs and other hardwares solve the problem and how it is different from CPU.

Note
Writing this piece is critical because we engineers are so accustomed in our world that we assume a lot of info and it becomes hard for someone new to understand things like CPU vs GPU. It will be a challenging piece explaining parallel processing and parallel+distributed heterogeneous computing to newbies.