The graph of a non-invertible function $f$ is shown below.
Also shown is a horizontal line which you can click and drag to different heights. If that line intersects the graph of the function $f\text{,}$ the point(s) of intersection will be shown.
Next, the graph of an invertible function $g$ is shown.
1. According to these graphs, what is true about the graph of an invertible function?
2. According to these graphs, what is true about the graph of a non-invertible function?