I always understood it as guiding the lightning through your body in a path that doesn’t kill you. I assume it has to be converted into an energy that doesn’t cook you along the way. The energy can’t just be absorbed or directly pass through sensitive points such as the heart, so it must sent back out, converting it back to lightning in the process.

I believe the energy conversion step is limited to a fire bender. If anyone tried this, they’d just fry themselves.

That’s how I think of it, no idea what cannon is.