Post codes, also known as zip codes, are a series of numbers and/or letters used to identify a specific geographic area. They are used by postal services to efficiently deliver mail and packages to the correct address. ETIQUETTE is the set of rules and conventions that govern social behavior. In the context of post codes, ETIQUETTE refers to the proper way to address an envelope or package. It is important to include the post code in the address to ensure that the mail or package is delivered to the correct location.