[c++] What does "#include <iostream>" do?

As I started learning basic C++, I've always used the headings

#include <iostream>
using namespace std;

I want to question what is the point of iostream. Is it required every time as a heading?

That is a C++ standard library header file for input output streams. It includes functionality to read and write from streams. You only need to include it if you wish to use streams.

# indicates that the following line is a preprocessor directive and should be processed by the preprocessor before compilation by the compiler.

So, #include is a preprocessor directive that tells the preprocessor to include header files in the program.

< > indicate the start and end of the file name to be included.

iostream is a header file that contains functions for input/output operations (cin and cout).

Now to sum it up C++ to English translation of the command, #include <iostream> is:

Dear preprocessor, please include all the contents of the header file iostream at the very beginning of this program before compiler starts the actual compilation of the code.