A literature review is a synopsis and synthesis of publications on a particular topic. It can have a few different purposes. One is to provide a backdrop for one's own research, and another, to simply provide one's audience or oneself of an overview of that topic. In the first instance, a review of the literature is one of the beginning sections in a thesis or dissertation on a topic. In the latter, the review of the literature stands alone as an academic paper.
No matter what the purpose is, a literature review begins with research into a particular topic. Today, most schools have access to an academic database that you can use to find articles in any discipline. These are what we call peer-reviewed articles, meaning that they have been reviewed by people who are competent in that particular discipline, ensuring to some degree the quality of the articles. As a general rule, when you are doing research for a literature review, you should be using only peer-reviewed articles.
A concrete example should help you see how this works. You might be writing a literature review for an education course and choose the topic of the use of cell phones in the classroom. You would find many articles on this topic. It is now up to you to choose the articles that you are going to write about in your literature review.
If your purpose is to write a stand-alone literature review, i.e., not in preparation to do your own research on this topic, then you will choose some articles that provide a good overview of the topic, perhaps including articles about this topic in different countries and articles that cover different ranges of student age groups, for example, middle school, high school, and college. You are likely to find articles that conclude that cell phones in the classroom are beneficial and also articles that conclude they are a terrible idea. To provide a balanced literature review, you would probably use both.
If your purpose is to write a literature review that is a backdrop to research you want to do yourself on the use of cell phones in the classroom, perhaps a survey of teachers you want to do or a survey of students, then you would include all of the above, and additionally, you want to identify what is missing from previous research on this topic, so that you can justify the need for the research you want to do. For example, you might find that there is a great deal of research showing what teachers' opinions are on cell phone usage in the classroom, but very little about student attitudes on this subject. This justifies the research you wish to do, to contribute to the knowledge base on the subject.
Once you have identified all of the articles you want to use, you must, of course, read them first. Then you are going to identify the ideas and information that you want to focus on in the literature review. For each idea that you want to explore in the literature review, you will write a section, which could be one paragraph or several paragraphs. You will use your sources, the articles, to present those idea. As you discuss an article, you need to give the reader a brief synopsis of the article, the nature of the research done, for example, the conclusion the author reached, and probably some details about the research, a study of many students, a study of just a few students, their age group, and the area in which the study took place. What you do not want to do is organize a literature review around to the articles you read. In other words, it is a mistake to have a paragraph on article A, a paragraph on article B, and so on. This is because you are expected to organize around ideas and points. This is meant to be a synthesis of all you have read, a means of compiling ideas and information and offering them to your reader in a new and fresh way. So, if I were writing about this topic, I might find several articles about how bad cell phones are in the classroom, and I would include all of these in a section on the negative aspect.
As you begin to put all of this together, you will want to remember that this is meant to be a purposeful review of the literature, to provide an overview, or to provide a backdrop to research you want to do. Every idea you discuss should be in aid of that purpose. If you use all of the principles that you would use for writing any essay, having a central idea and sections and body paragraphs that help the reader understand that idea, you will be able to do this more easily. Think of a review of the literature as a long essay that is a means of providing an overview on a topic and/or that shows the reader why your own research is going to be important.