A.SSE.1 Quadratic using vertex, focus and directrix

A.SSE.1 This applet is designed to help you discover the key features of a parabola: y-intercept, slope, vertex, focus, and directrix. By making changes to the slope and y-intercept, you can see how the equation, focus and directrix change and their relationships. Then when given only the focus, vertex or directrix, you can create the equation of the parabola.
What happens when you change the slope? The y-intercept? What is the relationship between the vertex, focus and directrix? What is the relationship between the segment distance from the vertex to either the focus or directrix and the slope?