求解答，一道容器类的题目

#include<iostream.h>
#include<string.h>
class Date
{
private:
int year;
int month;
int day;
public:
Date(int y,int m,int d){year = y;month = m;day = d;}
void show(){count<<"出生年月是"<<year<<"年"<<month<<"月"<<day<<"日"<<endl;}
};
class Person
{
private:
char Name[8];
Date date;
int h;
int w;
public:
Person(char *n1,int y1,int m1,int d1,int h1,int w1){
strcpy(Name,n1);
h = h1;
w = w1;}
void print();
};
person类中 Date date;什么意思。还有
Person(char *n1,int y1,int m1,int d1,int h1,int w1){
strcpy(Name,n1);
为嘛这里不用定义 y1 m1 d1 了