It's great to write your own shaders and effects so that you can fine-tune your project to look just the way that you want, and this is what we will be spending the majority of the book looking into. However, it's also good to point out that Unity already comes with some prebuilt ways to get some of the more common effects that users like to have through the use of the Post Processing Stack.
For those who just want to get something up and running, the Post Processing Stack can be an excellent way for you to tweak the appearance of your game without having to write any additional code. Using the Post Processing Stack can also be useful in showing you just what shaders can do and how they can improve your game projects as, behind the scenes, the Post Processing Stack is itself a shader that is applied to the screen, aptly called a screen shader.
