Point / Midpoint / Segment Definition APS

In the applet below, point M is said to be the midpoint of the entire segment you see. Interact with this applet for a minute, being sure to change the locations of the segment's endpoints each time before re-sliding the slider. After doing so, please answer the question below the applet.
The applet above dynamically illustrates the definition of a midpoint of a segment. Without using the words "half", "halfway", or "middle", explain what a midpoint of a segment is in your own words. That is, complete the following sentence definition: A midpoint of a segment is a... (If you're not sure, you can find a hint by clicking here).