A "Big Integer" is a data type used in computer programming to represent very large whole numbers that exceed the limits of standard integer types. While typical integers can only store values within a specific range, Big Integers can handle numbers with thousands of digits, making them useful for applications in cryptography, scientific calculations, and financial modeling. In many programming languages, such as Python and Java, Big Integer libraries or classes are available to facilitate operations on these large numbers. These libraries provide functions for arithmetic operations, comparisons, and conversions, allowing developers to work with large integers seamlessly without worrying about overflow errors.