what does this declaration mean? exception() throw()

Question

std::exception class is defined as follows

exception() throw() { }
virtual ~exception() throw();
virtual const char* what() const throw();

Answer 1

Without any parameter, it means that the mentioned functions does not throw any exceptions.

If you specify anything as a parameter, you're saying that the function will throw only exceptions of that type. Notice, however, this is not an enforcement to the compiler. If an exception of some other type happens to be thrown the program will call std::terminate().