texture is a plain 2d image while a shader is usualy a complex structure of nodes.
Load a shader and display it in the hypershader and u will see. A texture can be a or several nodes to come up with a final "texture"
SimplyMaya specialises in Maya tutorials. We offer over 1,000 individual Maya training videos, ranging from basic Maya tutorials through to intermediate Maya tutorials. Our tutorials are created by instructors with industry experience and are designed to get you up and running in Maya quickly without making it seem like hard work.