Say you textured a wooden cube in blender (with blenders own shader) then imported into unity, then unity would take the texture and fit it on one of unity's default shaders, depending on how many texture maps it comes in with (normal, shine, etc). You can then choose to change that default shader in the material slot with more specialized ones (there are quite a few shipping with unity), which you can edit by script. Or you can rely on others to make them or even construct them with shader-tools like strumpy, shader forge, etc.