Difference between "referee" and "reviewer" in the context of journal manuscript review?

So far as I have ever been able to tell, "referee" and "reviewer" mean exactly the same thing.

I think they are synonyms.

I guess there might be a very slight emphasis that a referee makes a decision, where a reviewer produces a report. But both do both, in the case of journals.

My experience is that usage varies. In my field, it is common to use 'referee' for the person who anonymously comments on a paper submitted to a journal, and 'reviewer' for the person who writes about a paper already published to appear publicly in a database. However, people I know in similar areas use 'reviewer' for the first meaning. To confuse things more, there are some discussions underway about changing the publishing model, which would have the effect of essentially combining these two situations.