I'm not in the triple A game design industry, more like some good grade, game-ish design industry, so what I have to say may not apply to the state of the art.
Generally, a material is made up of _several_ textures that serve different purposes. Common textures (often called 'maps') used to build materials are albedo maps, surface normal maps, metallic/roughness maps, subsurface scattering maps (this one is important for realistic looking human skin!). There's others, and sometimes aesthetics/requirements require shader authors to _make up maps_.
Consider a texture map just like, a precomputed data cache. You can encode pretty much anything in them. Why, in the gritty gore and carrion filled trenches, I've created systems where artists can use maps to annotate parts of models they think suck. That map was used in a camera AI system that tried to avoid looking at parts artists are ashamed of, adjust depth of field threshholds depending on the depth of bad stuff... That kind of thing. (That texture seam is too gross for the sizzle cinematic, there's NO TIME to fix it. Just smudge the camera, or have it lose focus as it sweeps through! shameMap.png to the rescue).
The limit to the kind of data you can _use_ is only your imaaaagination..
For people, for most aesthetics, at minimum you need a color or diffuse or albedo map.
Generally, a material is made up of _several_ textures that serve different purposes. Common textures (often called 'maps') used to build materials are albedo maps, surface normal maps, metallic/roughness maps, subsurface scattering maps (this one is important for realistic looking human skin!). There's others, and sometimes aesthetics/requirements require shader authors to _make up maps_.
Consider a texture map just like, a precomputed data cache. You can encode pretty much anything in them. Why, in the gritty gore and carrion filled trenches, I've created systems where artists can use maps to annotate parts of models they think suck. That map was used in a camera AI system that tried to avoid looking at parts artists are ashamed of, adjust depth of field threshholds depending on the depth of bad stuff... That kind of thing. (That texture seam is too gross for the sizzle cinematic, there's NO TIME to fix it. Just smudge the camera, or have it lose focus as it sweeps through! shameMap.png to the rescue).
The limit to the kind of data you can _use_ is only your imaaaagination..
For people, for most aesthetics, at minimum you need a color or diffuse or albedo map.