What is the work of iostream in c++

The I/O stream header is responsible for transferring streams of data to the output console. It also defines a way of receiving input through a console As its name suggests I -> Input O -> Output Stream -> data streams. Without the header "iostream", you can't receive input or print output

Ya'iko stdio.h/cstdio still exist with scanf and printf related functions, without iostream.

That's because C++ covers the entire C language. So any C code works well for C++