Return 0;

Question

can anyone please tell me what the return 0, does

Answer 1

The int value that main returns is usually the value that will be passed back to the operating system. 0 traditionally indicates that the program was successful.
You don't have to return 0 explicitly, because that'll happen automatically when main terminates. But it's important to keep in mind that main is a function where omitting return is allowed.

Answer 2

You self answered on your question