I'm pretty sure it's just the difference between a file being named foo.tar.gz and (SHA-256 of the file).tar.gz[0] - the content and storage are the same, it's just that the canonical name is a hash of the contents rather than being arbitrary.
[0] ex. 1324cca9ed1d8267363ef6c835ca251bd810c21c49b2acc00e02d607c95ef9ad.tar.gz