I have been visiting some journal websites and I found that some of them state that they use a double blind review process.
What does it mean?
It means that, not only are the reviewers' identities unknown to the authors (as usual), but the authors' identities are unknown to the reviewers. Only the editor(s) know the identity of everyone involved. This supposedly makes for a less biased review. This also means that the authors need to exercise special care in preparing the submission, because they should avoid all instances of "we" when referring to past, cited papers, for example.