What is the noise, exactly?

Is it the steel expanding and contracting that makes the noise when the fire is going? I get the steady tic, tic ,tic in the stove pipe as I heat things up or damper back down and a deeper tunk, tunk or thump, thump in the stove when it is heating up. You can actually feel the stove tunks if you are standing next to it. I am burning a VC Defiant.

Does anyone know what is actually happening other than "expand/contraction of steel" - or is that just it?

In a VC it would be cast iron not steel. Since the stove is bolted together, not one piece like a steel stove, the noise is likely uneven expansion, i.e., some parts heat up more than others and rub against each other in the process. So yes, "expand/contraction" but not of steel, of iron.

Your are hearing the heat making it's announcement that it has arrived! The noises you are hearing are normal. Sometimes you may hear a tic tic tic if the primary air flap on the back of the stove is opening and closing. All normal noises you do not need to be concerned about.

Thank you - assumed as much but like to be sure. I mean I do have a fire going inside my home!