Some lowercase Latin letters have parts that go over/under the text line: compare w with k and j.
The k has an upper part, and the j has a lower one. Do these parts have a name?
. The ‘Baseline’ is the (usually imaginary) line that most of a documents text/characters are sitting on.
. The ‘Capline’ is the (usually imaginary) line that marks the top of capital letters as well as the top of some lower case ascenders.
. The ‘X height’ is the (usually imaginary) line that marks the height part of the lower case letters disregarding the ascenders.
. Ascenders : part of a lower case letter that rises above the X-Height.
. Descenders : part of a letter that extends below the baseline.
I used the link provided by Billy Kerr for help with definitions : https://www.canva.com/learn/typography-terms/
Hopefully this is a helpful summation of a few terms and specifically ascenders / descenders in typography.