In the case of Materials, textures are simply images that provide some sort of pixel-based data. This data may be the color of an object, how shiny it is, its transparency, and a variety of other aspects. There is an old-school mode of thought that "texturing" is how you apply color to your game models. While the process of creating textures is still critical, it is important to think of textures as a component of Materials, and not as the end result themselves.  

A single material may make use of several textures that are all sampled and applied for different purposes. For instance, a simple material may have a Base Color texture, a Specular texture, and a normal map. In addition, there may be a map for the Emissive and Roughness stored in the alpha channels of one or more of these textures.  

You can see that, while these all share the same layout, the colors used are specific to the purpose of the texture.