JSON - how to convert variables it into text and vice versa (with Unity3D & PlayerPrefs)

Recently I used JSON a lot and I'd like to share some knowledge about it.

Here I'm using MiniJSON (link) because I prefer C# rather than JS (this one make me sick!).

So at beginning what JSON is?
JSON is a... string :) And it can have our arrays, dictionaries, variables and other crazy things. And this is all about it, but if you like reading you should go to Wikipedia and read all about it :P