I feel like “Another word for a shader” should be the correct answer, since exactly like a shader, materials don’t contain textures. they just utilize them. Just because the editor is graphical doesn’t make them any different from a standard shader. does it?
Hi,
You would probably be better off raising this on the Q&A against the course, the instructors don’t tend to frequent the forum and their are dedicated student instructors who can escalate your queries if you post on the Q&A.
Hope this helps 
The way I read the Unreal documentation, I understand that materials do contain both textures and shaders:
" While the process of creating textures is still critical, it is important to think of textures as a component of Materials…"
“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 Texture.”
Maybe the course is teaching us about Unreal’s materials, as opposed to materials in other engines or in graphics theory?