Shaders simply put are code that runs on the Graphics Processor to modify the graphics as you see fit. They run in parallel, allowing for far more complex algorithms to run than would be possible on a CPU, and they power the high end graphics that we see today in many games.
Okay, so first of all, what makes up a shader? There are two parts of all shaders which are critical to their functionality. The first is a vertex shader, which will modify the locations of the vertices. The second is a fragment shader, which works on a pixel-by-pixel level to make the appropriate changes. What is a simple example of one of these? Let's look to the Unity Documents for a simple example.
Next is the Shader itself. I'm not going to explain every line in the shader, but I will explain two key items. The function "vert" is the function that manages the vertices. "frag" manages the individual pixels. Essentially the vertexes are passed without interference, and the frag returns a uniform color, making the object appear a single color, no matter the angle viewed.
Next time I will go more in to depth about Unity 5's standard shader, and will go from there to cover some of the other features shader development.
Ben Pearson is the author of the Amateur Radio and other technology blog KD7UIY and developer of Games and Apps at Google Play pearsonartphoto, where he plans to publish some of the games created by inspiration of gamedev.tv. He is currently working on a Sea Trading game, which you can subscribe to updates at his Google Group. He has been a programmer since a young age, although only recently is learning programming with game engines. He has completed the the Complete Unity Developer Course and the Procedural Generation courses, and is working through the Complete Blender Developer Course and Unity Game Physics courses. He is hoping to soon start Unreal Courses soon. Follow him on Twitter @KD7UIY.