A broody is a hen that wants chicks. It's determined by hormones. Some hens go broody and some never do.
If your hen is broody she will go and sit in the nest box and usually only come off once a day or every other day. When she is off the nest they have a broody cluck that they make and repeat over and over and over...... Occasionally they will steam roll through other hens and scatter them because they are on a mission when they are broody and want to get their business done and be back on the nest. If you mess with them when they are on the nest they may growl at you, some might screech, most will peck the crap out of your hands, all of them I have ever seen (even the friendly broodies) will puff up their feathers in response to you. If you pull them out and set them on the ground they will remain fluffed up and in a spread out position. On the nest if you watch them and don't interrupt they tend to zone out and stare into space and react to very little until it gets close to the nest.
Personally the most dangerous birds to chicks are non-broody hens in my limited experience, others will probably advise you the same. If you want to introduce chicks and your birds aren't broody it will almost definitely end up with the chicks being killed. If you want to try and introduce them anyone on an off chance someone would want them, make sure you place a divider of some kind between them or something similar, where the hens can't get to the chicks and the chicks can't get to the hens. The hens will probably act interested in them, but that doesn't mean they won't try and peck them to death though.