Overshoot
Overshoots are optical size adjustments to make glyphs appear the correct size.
The overshoot is what it says it is. It’s the part of the letter that overshoots the baseline or the cap line to make the glyph size look optically correct.
As you can see in the bottom example, when I scaled the type to remove the overshoots, the size looks wrong. They’re mathematically the same height as the other letters but optically, they look smaller.