The expression -b \pm \sqrt{b^2 - 4ac} is part of the quadratic formula, which is used to find the solutions of a quadratic equation in the form ax^2 + bx + c = 0. Here, a, b, and c are coefficients, and x represents the variable. The term b^2 - 4ac is called the discriminant, which helps determine the nature of the roots. The \pm symbol indicates that there are generally two solutions: one where you add the square root and one where you subtract it. If the discriminant is positive, there are two distinct real roots; if it is zero, there is one real root; and if it is negative, the roots are complex numbers.