Found in iostream.h, this C++ command is used to output stuff to the screen.

Usage:
cout << "Hello, World!";

To output a variable you do
cout << varname;
and to do a variable and string together you do
cout << "Hello, World! My favourite number is " << varname << ". I also like cheese.";

This, of course, assumes that you like cheese (surely you do!) and that varname contains your favourite number.