From cppreference.com
back_insert_iterator&operator*();(until C++20)constexprback_insert_iterator&operator*();(since C++20)Does nothing, this member function is provided to satisfy the requirements of
.
It returns the iterator itself, which makes it possible to use code such as *iter=value to output (insert) the value into the underlying container.
Parameters
(none)
Return value
*this