Quoting from two book's here

Book 1

"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.."

Book 2
" 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.