Every digital can create a hash, which is automatically generated depending on the algorithm you use. If you open up a text file, have nothing in it, it will have one hash, you write the letter a, it will be completely different, write the letter b, it will be completely different again.
So no, two hash files can’t have the same hash, but that’s not to say it isn’t possible, but it’s very rare. See http://en.wikipedia.org/wiki/Hash_collision
Hashing is also used in security to see if the file has been modified. If it has, it would create a different hash value. See http://en.wikipedia.org/wiki/Watermark_(data_file) and http://en.wikipedia.org/wiki/Cryptographic_hash_function