The equation "ax² + bx + c = 0" is a standard form of a quadratic equation, where a, b, and c are constants. The variable x represents an unknown value. The term a cannot be zero, as this would make the equation linear instead of quadratic. Quadratic equations can have zero, one, or two solutions, which are the values of x that satisfy the equation. To find the solutions, one can use the quadratic formula, which is x = (-b ± √(b² - 4ac)) / (2a). The expression under the square root, b² - 4ac, is called the discriminant and determines the nature of the solutions. If it is positive, there are two real solutions; if zero, there is one real solution; and if negative, there are two complex solutions.