Quoting from two book's here
"Shading is the term in Maya software for applying colours and textures, knows as shaders, after you model your objects...
Shading is the proper term for applying a renderable colour, surface bumps etc, Texturing is formally used when applying a map....
The porcess of shading is often refered to as texturing
A shader is a material node such as the Lambert, Blinn, Phong.."
" Texturing generall refers to the process of building a surfaces detail indicating how that surface will react to light.."
I looks to me that there is a difference as Magicsy said but it appears that the terms are pretty much interchangable, depending who you talk too.