This is the line that prints out the text string, "Hello, World!". You can print out any series of text strings by separating them with <<. So, instead of saying cout << "Hello, World!" << endl;
you could say
cout << "Hello, " << "World" << "!" << endl; The endl simply adds a carriage return (stands for "end-line").
A simple program
cout
//include this file for cout
#include <iostream.h>
int main()
{
//print out the text string,
//"Hello, World!"
cout << "Hello, World!"
  << endl;
return 0;
}
For now, don't worry about how cout works, just know how to use it.