They blow out their feathers (some drastically all over, some sparsely all over, some in patches) in order to grow new ones in. In more severe molts they look like porcupines with patches of pinfeathers filling in the bare spots. The sensation of pinfeathers pushing through the skin seems to be very irritating so chickens do not like being handled or touched during molt, and may get cranky with one another as well.
You will see decreased or a complete stop in laying.
Increasing protein can help with new feather growth but other than that, best to just minimize handling as much as possible and let nature do what nature does.
I have 11 birds going through various stages of molt right now. Some look almost bald and some just like they got a little mussed. I try to give them more meal worm snacks an other proteins to help with new feather formation. Some are still laying regularly and some arent. I just hope they all get their new feathers before the weather gets too cold. I lost 2 girls that decided to molt in december last year. We live in ny so we have really ccold winters.
Thank you all for your answers. I was starting to get really worried about 2. Mainly cause one was the healthiest fatest happiest and now shes miserable and my other one is 10 and started looking how you said like a porcupine.