Focus and directrix of a parabola

Find the focus and directrix of the parabola $y = \dfrac{x^2}{4}$. Rewriting it as $x^2 = 4y$ matches the form $x^2 = 4py$ with $p = 1$, so the focus is $(0, 1)$ and the directrix is the line $y = -1$.

Every point on the parabola is equidistant from the focus and the directrix. For instance the point $(2, 1)$ is $\sqrt{2^2 + 0^2} = 2$ from the focus $(0, 1)$ and $1 - (-1) = 2$ from the directrix $y = -1$. The large dots mark the focus $(0, 1)$ and the parabola points $(2, 1)$ and $(-2, 1)$.