I realize I didn't answer your question, but I wanted to find out if you knew what channeling was as opposed to mediumship.
And yes of course mediums can be channelers and channelers can be mediums. It is just, most like to specialize in one or the other, but they can be both.
The reason I think they are different is probably only in my imagination, but if you were to as a medium if they are a channeler, in my experience the answer is no.
So I guess it is mostly a personal difference.
Since I am not a medium (and don't wish to be) I can't say for sure.
However, someone I know and love is both and likes to be both, so there you are. My scientific study proved wrong
While I am fascinated by mediums and their gifts and the information they bring through, I think that would be a more difficult way to live until they learn to shut it down at will.
As to your original question: "I wanted to know primarily what it is for those who say they are channelers" you asked WHAT it is, so I was trying my best to explain what channeling was, from my perspective of course, which is the only one I have.
I would imagine channeling means something different to everyone that channels, because we only have our own tiny perspective.
Are you a medium asking about channeling, or are you a scientist trying to determine (using a scientific method of course) what is channeling? I'm just curious.