Can you guys tell me what is the difference between header <iostream> and <stdio.h> ?

Answer 1

stdio.h is the header file used for input/output in the C standard library.
iostream is the input output class in C++

Answer 2

stdio.h and iostream have deferent methods included in them and are used for deferent purposes. The in/out methods for stdio.h are mainly print() and scan(), for iostream, cin and cout.

While cin/cout is more easy to use, scan/print is quicker. (Not a notable difference in small data sizes)

You can use both in c++ depending on the situation but iostream is recommended.