The pursuit of a literature review is to demonstrate the reader, whether it is your professor or a large audience that you have read thoroughly and can be a good judge of a published work that has to do with the area of your interests. This kind of paper doesn't have a defined format and is allowed to include online sources of information. It can be a separate research paper, devoted specifically to the review, but also it can be a part of other research paper, like a report or a dissertation.
Let us make it clear from the beginning that a review is not a description of a publication written by someone else and it's not a summary. Clearly, it is a critical discussion, which provides reader with valid arguments concerning a proper publication, as well as demonstrates that you have a deep understanding of various theories and approaches.