A zip code is a series of numbers used by postal services to identify specific geographic areas for mail delivery. In the United States, a standard zip code consists of five digits, which help sort and route mail more efficiently. For example, a zip code can indicate a particular city or neighborhood, making it easier for postal workers to deliver letters and packages to the right locations. Zip codes can also be useful for various purposes beyond mail delivery. Businesses often use them to determine service areas, while online retailers may use them to calculate shipping costs. Additionally, zip codes can help in demographic studies, allowing researchers to analyze population trends and characteristics in different regions.