Completing the square is a mathematical technique used to transform a quadratic equation into a perfect square trinomial. This method helps in solving equations of the form ax^2 + bx + c = 0 by rewriting it as a(x - p)^2 = q, where p and q are constants. This makes it easier to find the roots of the equation. To complete the square, you first divide the equation by a (if a is not 1), then rearrange the equation to isolate the constant term. Next, you take half of the coefficient of x, square it, and add it to both sides of the equation. This process allows for easier graphing and understanding of the quadratic function.