Answer 1

I’ll try to explain this as best I can: Class hierarchy is like a family tree, in a way. There’s the oldest (referred to as the “parent” in programming) and younger ones (referred to as the “child”). If you need more, think of it like fish. There’s the biggest fish eating smaller fish (a parent over the child). You can read a better explanation here:
http://www.modernescpp.com/index.php/c-core-guidelines-class-hierarchies
Here’s a diagram too, to help:
https://www.programtopia.net/sites/default/files/heirar_1.png