A cold chisel is used to remove excess or unwanted metal in situations where the finish does not need to be very smooth. It's called a cold chisel because it's not meant to be used with heating tools or hot metal.
Cold chisels have a cutting edge on one end, and they are generally meant to be struck with a hammer at the other end to drive the chisel into the material. Cold chisels come in a variety of types, including flat, round nose, cross cut and diamond point. All these chisel types come in a wide variety of sizes.