An Externality is a benfit incurred by a group that diddn’t agree to the action that made that benefit. Externalities can be bad to gerneral economy, because they allow production of a product that may not have been entirly wanted. An example could be burning coal for fuel. While the burnt coal will allow a machine to run, the externatlity, smoke, could cause medical problems to a work force mantaining the machine. While not all externalities are as unsatisfying, it is important to reconize any changes that could cause them in the market.