Sometimes called Dungarees, Overalls are traditionally made from denim and typically worn over the top of your ordinary Workwear. They are designed to protect your clothing from becoming damaged whilst in the workplace, for example preventing the clothing from being covered in paint or varnishes.
Overalls are normally long, so that they fully cover your trousers. They also have shoulder straps that can easily be done up and undone, allowing you to choose whether you cover your chest or not. This also makes removal of the Overalls incredibly easy, which is useful when they are dirty.