A virtual function lets you override a method in a child class, and have that child version actually get called even when you’re using a pointer or reference to the base class.

In short:
Use the correct version of a function, no matter what type of pointer you're holding.

This is the case of runtime polymorphism.

• It’s how C++ picks the right function at runtime.
• Lets you treat objects generically but still get custom behavior.
• Without it, the base class version always gets called.

#include <iostream>
using namespace std;

class Animal {
public:
    virtual void speak() {
        cout << "Animal sound." << endl;
    }
};

class Dog : public Animal {
public:
    void speak() override {
        cout << "Woof!" << endl;
    }
};

int main() {
    Animal* a = new Dog();
    a->speak();  // Outputs: Woof!
    delete a;
    return 0;
}