A more clear difference would be Invocation versus Evocation. The term summoning refers to the practice of either, while channeling is less used term in my experience. When I hear channeling I'm under the impression you are referring to something like a seance.
Invocation is the art of calling a spirit, entity, deity or what ever it is you are calling upon and then bringing it thru yourself as a medium. For instance, some people will draw upon the elements and invoke those forces within themselves.
Evocation is the practice of drawing a spirit, entity, deity or what ever it is you are calling into a space outside of yourself. If you read the goetia for instance, that is evocation with the use of a magick circle and binding emblem to call upon demonic spirits into a space.
So the difference between Evocation and Invocation is basically this, one summons into a space, and the other summons into your body or spiritual self depending on the exact working, respectively.