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Shaders are text files loaded by the engine and compiled onto the GPU for changing how textures and models look at run time. Note that Mobile is mobile GLSL so slightly different. Additionally NVIDIA, Intel and AMD may be compatible with shaders in different ways. Worth testing on every platform you can.
There's really just a few real separate shaders. The vs and fs prefixed files just have key flags that get turned on and off to make the shaders do different things, like yes or no use normal, spec, roughness, etc. In general the VS ones get your vertex properties all set up. The FS ones basically paint your screen pixels using the information gleaned from the nearest verts. And then there's a post-processing layer that does your stuff like sharpen and screen depth type stuff. And finally there's your shadow and beaming projectors.
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