Answer 1

Here’s an answer off the web:
IOstream is a library package which support all basic input output operation such as printing data, collecting input from user, creating class, etc. istream is directly associated with keyboard and ostream with monitor.

Namespace std

Namespace is a region that provide scope to identifier, function, variable to avoid collision. You can declare same variable in different namespace.

std also known as standard is only namespace available in C++, but you can create your own namespace.

cout, cin, max(), min(), _gcd() etc all these are defined in std namespace.

If you do not write using namespace std then you have to use std::cout, std::cin etc everywhere.

So basically both are different thing so we can’t distinguish each other.