It is complete normal for hens to roll eggs underneath them when they are laying - it an evolutionary process to keep all the eggs in one place so they can hatch them together in a safe place. It’s just instinct - it doesn’t mean your hen is broody. A broody hen will sit in her eggs all day long, only leaving once or twice a day to poop / eat / drink. They will also hiss and peck at you if you try and disturb them. This is something normal though - all my chickens roll the existing eggs underneath them while they lay.
In order for there to be a chick in there, you would have to have a rooster. Once the egg is fertilized, it requires purposeful incubation before it will hatch. But the chickens don’t know if the eggs are fertilized or not - a broody hen will sit on a pile of rocks if you let her.