If the discriminant of a quadratic equation is equal to zero (b^2 - 4ac = 0), there is one real root which is repeated. Moreover, there is also just one x-intercept.
If the discriminant is positive (b^2 - 4ac > 0), there are two real roots; and if the discriminant is negative (b^2 - 4ac < 0), there are two complex roots.
