Why use member variables over instance variables?

Question

Why use member variables over instance variables?

Answer

Member variables are those that you want to be the same across all objects of a class. In our Animal example, all animals should be alive, so we set is_alive = True as a member variable.
However, things that might differ from animal to animal are their name and age! So for those things that are not the same across the board, we create instance variables.