A signed integer is a type of data representation that can hold both positive and negative whole numbers. It uses one bit to indicate the sign of the number, where typically 0 represents positive and 1 represents negative. This allows for a range of values, usually from -2,147,483,648 to 2,147,483,647 in a 32-bit system. In computer programming, signed integers are commonly used in various applications, such as calculations and data storage. They are part of the broader category of integers, which also includes unsigned integers that can only represent non-negative values. Understanding signed integers is essential for effective programming and data manipulation.