Function overriding versus overloading

Function overloading means having several functions with the same name in the same scope but different parameter lists (number, type or order of parameters). Function overriding means a derived class redefines a base class function that has the same name, return type and parameters.

Example of overloading:

class Calc {
public:
    int add(int a, int b)       { return a + b; }
    double add(double a, double b) { return a + b; }   // different types
};

Example of overriding:

#include <iostream>
using namespace std;

class Animal {
public:
    virtual void sound() { cout << "Some sound" << endl; }
};
class Dog : public Animal {
public:
    void sound() { cout << "Bark" << endl; }   // overrides Animal::sound
};

int main() {
    Animal *p = new Dog;
    p->sound();          // Bark (decided at run time)
    delete p;
    return 0;
}