partial class == abstract == method overriding ?

Question

partial class : using parital class we can extend the logic.

abstract: we can create abstract method that can implemented in child class.

override: we can recreate a method in child class and make it as seperate method.

 

why we have these many things for doing same job?

 

please give simple reply don't make me confuse.

 

one interviewer ask me, if partial class can extend method whey you want to use abstract class for futre implementation.