Concrete Products (Windows & Mac):?

Short answer: WindowsButton, MacButton, WindowsCheckbox, and MacCheckbox are concrete implementations of the IButton and ICheckbox interfaces. Each one provides a platform-specific rendering logic. public class WindowsButton : IButton

Example code

{
public void Render() => Console.WriteLine("Rendering Windows Button."); }
public class MacButton : IButton
{
public void Render() => Console.WriteLine("Rendering Mac Button."); }
public class WindowsCheckbox : ICheckbox
{
public void Render() => Console.WriteLine("Rendering Windows Checkbox."); }
public class MacCheckbox : ICheckbox
{
public void Render() => Console.WriteLine("Rendering Mac Checkbox."); }

Real-world example (ShopNest)

Use a GoF pattern in ShopNest only when it removes duplication or makes a change safer—explain the problem it solves in the interview.

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.