The term "-1" represents a negative integer in mathematics. It is one less than zero and is used to indicate a value that is below zero. Negative numbers, including -1, are essential in various mathematical operations, such as subtraction and in representing debts or losses. In the context of number lines, -1 is positioned to the left of 0. Negative integers like -1 are often used in programming and computer science, where they can signify errors or specific conditions. Understanding negative numbers is crucial for grasping concepts in algebra and other areas of mathematics.