How do interfaces support abstraction?

Short answer: By exposing method signatures only, interfaces hide the implementation. Allows multiple classes to implement the interface differently, providing flexibility and decoupling. class Bird : IFlyable

Example code

{
public void Fly() => Console.WriteLine("Bird is flying");
}
class Airplane : IFlyable
{
public void Fly() => Console.WriteLine("Airplane is flying");
}

Real-world example (ShopNest)

Checkout calls IPaymentGateway.Charge(). Razorpay and Stripe adapters implement the same interface, so ShopNest can switch gateways without rewriting the order service.

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.