A ZIP code is a series of letters and numbers used by the United States Postal Service (USPS) to identify specific geographic areas for mail delivery. The term "ZIP" stands for "Zone Improvement Plan," which was introduced in 1963 to improve the efficiency of mail sorting and delivery. Each code typically consists of five digits, with an optional four-digit extension for more precise locations. ZIP codes help organize mail routes and ensure that letters and packages reach their intended destinations quickly. They can also be used for various purposes, such as determining sales tax rates, planning service areas, and analyzing demographic data in specific regions.