What exactly are replacement shaders?

Hi,

I want to use the function camera.SetReplacementShader for my minimap.
I am very new to writing shaders, but every shader I use, exept the shaders from this site, don’t seem to work:

http://forum.unity3d.com/threads/81437-Rendering-with-Replaced-Shaders

Everything is pink. every shader I use makes everything look pink.
On the forum (from the link) they talk about replacement shaders, but I can’t find anything about it on the internet…

You really need to know that I am a noob in shader writing, so maybe some of you know some good tutorials to write these “replacement shaders”?

You must pass a value to it.
Example: Rendering objects marked with an effect of “heat vision”
camera.SetReplacementShader (heatVisionShader “VisibleWithHeatVision”);