The transcript is about computer science inheritance concept. And the English is written very poorly. It is not easy to understand in English, if you apply it to this kind of abstract computer science concepts nobody will understand.
Inheritance allows for reuse of code where common behavior is defined once for a number of related classes and unique behavior is implemented only in classes where the behavior is different.
I don't think the marked bold one correspond to each other very much.
I think the following will be easier for you to understand.
I hope that you have the basic computer science or programming knowledge before you do this kind of translation, or it will be very difficult for you to translate the whole passage! For reference you can take chinese wikipedia of 继承_(计算机科学).
Hope that helps!