BigInt is a data type in programming that allows for the representation of integers larger than those typically handled by standard number types. While regular integers can only store values up to a certain limit, BigInt can manage very large numbers, making it useful for applications like cryptography, scientific calculations, and financial systems. In languages like JavaScript, BigInt is created by appending "n" to the end of a number or by using the BigInt() constructor. This feature enables developers to perform arithmetic operations on large integers without losing precision, ensuring accurate results in calculations involving big numbers.