What is the base class and derived class?

Short answer: Base Class (Parent) → Class whose members are inherited. Derived Class (Child) → Class that inherits from base class. class Vehicle { public void Start() {} } // Base

Example code

class Car : Vehicle {} // Derived

Real-world example (ShopNest)

ShopNest has a base PaymentMethod with virtual decimal Fee(). UpiPayment and CardPayment override the fee logic without changing the checkout caller.

Say this in the interview

1. Define — one clear sentence (the short answer above).
2. Example — relate it to a project like ShopNest or your real work.
3. Trade-off — when you would not use it.