I believe the above arguments say , construct an object istream_iterator<char>(inputFile) where it is an iterator that "point" to the inputFile which should be an istream class and whenever we do a ++ we read one char into variable. The other object istream_iterator<char>() should be the end-of-file indicator.
It is like open the inputFile (istream class) and read char one by one until detect end-of-stream stop. Those char read should most likely be stored somewhere for retrieval later on.