Непонятна тема (Классы содержащие другие классы, как данные члены )

#include <iostream>
class Point
{
public:
    void SetX(int x)  {
        itsX = x;
    }
    void SetY(int y)  {
        itsY = y;
    }
    int GetX()  {
        return itsX;
    }
    int GetY()  {
        return itsY;
    }
private:
    int itsX;
    int itsY;
};
class Rectangle
{
public:
    Rectangle (int top, int left, int bottom, int right);
    ~Rectangle() {}
    int GetTop()  {
        return itsTop;
    }
    int GetLeft()  {
        return itsLeft;
    }
    int GetBottom()  {
        return itsBottom;
    }
    int GetRight()  {
        return itsRight;
    }
    Point GetUpperLeft()   {
        return itsUpperLeft;
    }
    Point GetLowerLeft()   {
        return itsLowerLeft;
    }
    Point GetUpperRight()   {
        return itsUpperRight;
    }
    Point GetLowerRight()   {
        return itsLowerRight;
    }
    void SetUpperLeft (Point Location)
    {
        itsUpperLeft = Location;
    }
    void SetLowerLeft (Point Location)
    {
        itsLowerLeft = Location;
    }
    void SetUpperRight (Point Location)
    {
        itsUpperRight = Location;
    }
    void SetLowerRight (Point Location)
    {
        itsLowerRight = Location;
    }
    void SetTop (int top)  {
        itsTop = top;
    }
    void SetLeft (int left)  {
        itsLeft = left;
    }
    void SetBottom (int bottom) {
        itsBottom = bottom;
    }
    void SetRight (int right)  {
        itsRight = right;
    }
    int GetArea ();
private:
    Point itsUpperLeft;
    Point itsLowerLeft;
    Point itsUpperRight;
    Point itsLowerRight;
    int itsTop;
    int itsLeft;
    int itsBottom;
    int itsRight;
};
Rectangle::Rectangle(int top, int left, int bottom, int right)
{
    itsTop = top;
    itsLeft = left;
    itsBottom = bottom;
    itsRight = right;
    itsUpperLeft.SetX(left);
    itsUpperLeft.SetY(top);
    itsUpperRight.SetX(right);
    itsUpperRight.SetY(top);
    itsLowerLeft.SetX(left);
    itsLowerLeft.SetY(bottom);
    itsLowerRight.SetX(right);
    itsLowerRight.SetY(bottom);
}
int Rectangle::GetArea()
{
    int Widht = itsRight - itsLeft;
    int Height = itsTop - itsBottom;
    return (Widht * Height);
}
int main()
{
    Rectangle MyRectangle (100, 20, 50, 80);
    int Area = MyRectangle.GetArea();
    cout << "Area: " << Area << '\n';
    cout << "Upper Left X Coordinate: ";
    cout << MyRectangle.GetUpperLeft().GetX();
    return 0;
}

Rectangle MyRectangle (100, 20, 50, 80);

Rectangle (int top, int left, int bottom, int right);

Rectangle::Rectangle(int top, int left, int bottom, int right)
{
    itsTop = top;
    itsLeft = left;
    itsBottom = bottom;
    itsRight = right;
    itsUpperLeft.SetX(left);
    itsUpperLeft.SetY(top);
    itsUpperRight.SetX(right);
    itsUpperRight.SetY(top);
    itsLowerLeft.SetX(left);
    itsLowerLeft.SetY(bottom);
    itsLowerRight.SetX(right);
    itsLowerRight.SetY(bottom);
}

    itsUpperLeft.SetX(left);
    itsUpperLeft.SetY(top);

SetUpperLeft (Point Location)

    itsUpperLeft.SetX(left);
    itsUpperLeft.SetY(top);

#include<iostream.h>
#include <vcl.h>
#pragma hdrstop
#pragma argsused
class point{
public:
void SetX(int x){a=x;}
int GetX(){return a;}
int SetY(){return b;}
void SetY(int y){b=y;}
private:
int a;
int b;        };
 class tochka{
public:
tochka(int x,int y);
~tochka(){}
point Vozvrat(){return parametr;}
private:
point parametr;};
tochka::tochka(int x,int y){
parametr.SetX(x);
parametr.SetY(y);
                  }
int main(){
tochka koordinat(5,5);
cout<<koordinat.Vozvrat().GetX();
Sleep(1000);
        return 0;
             }