The equation "X = -1" indicates that the variable X is equal to negative one. This means that in any mathematical context where X is used, it will represent the value of -1. This can be useful in solving equations or understanding relationships between numbers. In a number line, -1 is located to the left of 0, indicating it is a negative number. Negative numbers, like -1, are used in various fields, including mathematics, finance, and science, to represent values less than zero, such as debts or temperatures below freezing.