A review is another level of filtering.
Its being used by the RAF at the moment as they're reducing recruitment numbers. So whereas they would run an OASC and make offers/rejections the week after (or whatever), they are now putting any offers forward to a review board. This review board will 'review' all would-have-been offers from over the last 3 (?) months, and pick the best 10% - or however many they need.
Some branches (i.e. medical etc.) aren't goign to review boards as the RAF is gasping for them!!
Hope that helps!!