A refereed journal has an established editor, editorial board and reviewer panel. Submitted manuscripts are subject to a 'blind' review process whereby authors and reviewers are unknown to each other to try to eliminate bias and make the decision to reject or accept a manuscript as balanced and objective as possible across the opinions of a number of 'experts'. With non-refeeed journals some, or all of these processes, are absent. The decision to accept or reject a manuscripts is often based on an individual's decision and/or the 'commercial' decision of the journal.
A refereed journal has an established editor, editorial board and reviewer panel. Submitted manuscripts are subject to a 'blind' review process whereby authors and reviewers are unknown to each other to try to eliminate bias and make the decision to reject or accept a manuscript as balanced and objective as possible across the opinions of a number of 'experts'. With non-refeeed journals some, or all of these processes, are absent. The decision to accept or reject a manuscripts is often based on an individual's decision and/or the 'commercial' decision of the journal.
If the editor of the journal sends your manuscript to two or more readers in the field for their considered views on whether your paper is publishable, and they agree that it should be published, then you have a peer-reviewed paper. Otherwise it is a non-refereed paper.
Ian is correct - but some journals will try to create the 'illusion' that they are refereed. They may well identify an editorial board. However, if you know your discipline well - you would expect to know and recognise at least a few of the names as established experts. That said, and they do not have to be predatory journals, but some journals will be 'new' journals with good intentions. However, the difficulty for many emerging journals is that they may find it difficult to recruit 'big names'. At least the editor, however, should be reasonably well known. Another thing to look for is 'is the editorial board international'. Also be suspicious if all the board are from the same country and similar institutions. Some journals may also 'pretend' that they are sending your manuscript out to review. There are many signs to look for with 'unscrupulous' journals - but some are the obvious ones i.e. no editorial board, no review process, poor online site construction, poor instruction, no robust submission process, demanding payment up-front etc.