这句话怎么解释？

这句话怎么解释？parent *p=new son(); 请指教

#include<iostream>
using namespace std;
class parent
{
public:
    virtual void foo()
    {
        cout<<"foo from parent."<<endl;
    }
    void foo1()
    {    
        cout<<"foo1 from parent."<<endl;
    }
};
class son:public parent
{
public:
    void foo()
    {
        cout<<"foo from son."<<endl;
    }
    void foo1()
    {    
        cout<<"foo1 from son."<<endl;
    }
};
int main()
{
    parent *p=new son();
    p->foo();
    p->foo1();
    return 0;
}