A laying hen will go into the nesting box and get down to business. A layer will leave the nest soon after laying an egg.
A broody hen will stay in the box, spread her body out, and stay for sometimes days at a time. The may leave for short potty breaks or to eat & drink. Then they go right back to the nest. They will often move eggs from other boxes if possible. They will sit on golf balls, rocks, sometimes nothing, and of course eggs. Even hens without roosters to fertilize eggs will go broody. They have an attitude. They will bawk, squawk, and bite at your hand if you come near her. If left to brood they go into what looks like a trance.
Put "broody hen" in the search line. I recommend "Old Fashioned Broody Hen Hatch A Long" There is great information on the first page, post 2.
Good luck to you.