
Bowl:The rounded form that describes a counter, may be either open/closed. Beak: The half-serif finish on some horizontal arms. Barb: The half-serif finish on some curved stroke. Ascender: Portion of the stem of a lowercase letterform that projects above the median. Arm: Short strokes off the stem of the letterform, either horizontal/inclined upward. Apex (above)/Vertex (below): The point created by joining two diagonal stems. Stroke: Any line that defines the basic letterform.
Hence, the ascender height was added to create an optical illusion of balance. It was due to the reason that some of the letters (Like uppercase letter M) may have a bigger text size which took up more space on the top which will cause the letter "h" looked smaller and shorter.
Vinod said that a lot of us don't know that the reason to have an ascender height (for lowercase letter h) that exceeded the cap-height in an inconspicuous way.