Before we get started we need to explain how the typical development flow works in dApp development, and the reasons it is set up this way.
A private net is a local blockchain that mimics the real blockchain, but you get unlimited cryptocurrency and it also runs much faster. Of course that cryptocurrency is not of any value outside of your private net, but this allows you to freely test and develop your dApp.
This is the first step, getting things running locally on your machine.