Exploring the graph of:
with varying values for a
an animation allowing a to vary from 5 to 5

Notice the yintercept is always at (0,2).

When the values of a are negative there is a parabola that points down but when the values of a are positive the parabola points up.

As the absolute value of a increase the parabola become more narrow.

When the parabola points down the vertex has positive x values

When the parabola points up the vertex has negative x values