A zip code is a series of letters and/or numbers assigned to specific geographic areas to facilitate the sorting and delivery of mail. In the United States, a zip code typically consists of five digits, with an optional four-digit extension for more precise locations. This system helps postal services efficiently route mail to its destination. Zip codes are also used in various applications beyond mail delivery, such as determining sales tax rates, identifying service areas for utilities, and analyzing demographic data. They can help businesses target marketing efforts and assist individuals in finding local services or resources based on their location.