Mit jelent ez a sor? C++

/*Ezt a sort nem értem:

Cat *pRealCat = dynamic_cast<Cat *> (Zoo[i]);

---------

A 24 órás könyvből tanulok.*/

//main.cpp

# include <iostream>

typedef unsigned short ushort;

typedef unsigned int uint;

using namespace std;

class Mammal {

public:

Mammal(short age): itsAge(age) { cout <<"Mammal Konstruktor \n"; }

Mammal(const Mammal &rhs);

virtual ~Mammal() { cout <<"Mammal virtual Destruktor \n"; }

virtual Mammal* Copy()const { return new Mammal(*this); }

virtual void Speak()const { cout <<"Mammal beszel \n"; }

void SetAge(short age) { itsAge = age; }

short GetAge()const { return itsAge; }

protected:

short itsAge;

private: };

Mammal::Mammal(const Mammal &rhs): itsAge(4) {

cout <<"Mammal copy Konstruktor \n"; }

class Dog: public Mammal {

public:

Dog(short age): Mammal(age) { cout <<"Dog Konstruktor \n"; }

Dog(const Dog &rhs);

virtual ~Dog() { cout <<"Dog virtual Destruktor \n"; }

virtual Mammal* Copy()const { return new Dog(*this); }

virtual void Speak()const { cout <<"Vau,vau \n"; }

protected:

private: };

Dog::Dog(const Dog &rhs): Mammal(rhs) {

cout <<"Dog copy Konstruktor \n"; }

class Cat: public Mammal {

public:

Cat(short age): Mammal(age) { cout <<"Cat Konstruktor \n"; }

Cat(const Cat &rhs);

virtual ~Cat() { cout <<"Cat virtual Destruktor \n"; }

virtual Mammal* Copy()const { return new Cat(*this); }

virtual void Speak()const { cout <<"Miau,miau \n"; }

void Purr()const { cout <<"prrrrrrrrrrr \n"; }

protected:

private: };

Cat::Cat(const Cat &rhs): Mammal(rhs) {

cout <<"Cat copy Konstruktor \n"; }

int main() {

const short numberMammal = 3;

Mammal *Zoo[numberMammal];

Mammal *pMammal = NULL;

short choice,i;

for(i = 0;i < numberMammal;i++) {

cout <<"(1)Dog,(2)Cat: ";

cin >> choice;

if(choice == 1)

pMammal = new Dog(2);

else

pMammal = new Cat(2);

Zoo[i] = pMammal; }

cout << endl;

for(i = 0;i < numberMammal;i++) {

Zoo[i]->Speak();

Cat *pRealCat = dynamic_cast<Cat *> (Zoo[i]);

if(pRealCat)

pRealCat->Purr();

else

cout <<"Huha ez nem macska \n";

delete Zoo[i];

cout << std::endl; }

return 0; }