Practically all human knowledge can be found in published or unpublished sources. Man builds upon the accumulated and recorded knowledge of the past. His constant adding to the vast store of knowledge makes possible progress in all areas of human endeavour. The investigator can ensure that his problem vacuum and that considerable work have already been done on topics which are directly related to his proposed investigation. For any specific research project to occupy this place in the development of a discipline, the researcher must be thoroughly familiar with both previous theory and research. To assure this familiarity, every research project has as one of its early stage, a review of the theoretical and research literature. A literature review is based on the assumption that knowledge accumulates and that we learn from and build on what others have done. Scientific research is a collective effort of many researchers who share their results with one another and who pursue knowledge as a community. Today’s studies build on those of yesterday. Researchers read studies to compare, replicate, or criticize them for weaknesses. A good literature review gathers information about a particular subject from many sources that are relevant to the topic area. It is expected to be well written and contains few if any personal biases. It should contain a clear search and selection strategy. Good structuring is essential to enhance the flow and readability of the review. Referencing should be accurate throughout the literature review, accurate use of terminology is important and jargons should be kept to a minimum. Therefore, from the above background, this manuscript gives a detailed explanation of each of the following: literature review, its importance,