Answer 1

Consider:

int function()
{
return 0;
}

int main()
{
cout << function();
}

// outputs 0

The return keyword is used by functions to return a value back to where they are called. Different types of function have different return values and types. E.g.

char function()
{
return 'a';
}

bool function()
{
return true;
}

etc.

In main(), the value 0 is returned to the operating system, signalling that the program has run successfully.