Are surcharges illegal?

Could you elaborate on the concept of surcharges and the legality surrounding them? Are surcharges, in general, considered illegal, or does it depend on the specific context or industry in which they are applied? Are there any specific laws or regulations that govern the use of surcharges? Furthermore, are there any penalties for businesses or individuals who violate these laws or regulations? Understanding the legality of surcharges is crucial for consumers and businesses alike, so I'm eager to learn more about this topic.