The expression "b² - 4ac" is known as the discriminant in the context of quadratic equations, which are typically written in the form ax² + bx + c = 0. This formula helps determine the nature of the roots of the equation. If the discriminant is positive, there are two distinct real roots; if it is zero, there is exactly one real root; and if it is negative, the roots are complex or imaginary. In practical applications, the discriminant is useful in various fields, including mathematics, physics, and engineering. It allows for quick assessments of solutions without needing to solve the entire equation, making it a valuable tool for analyzing quadratic relationships.