Literature searching is the task of finding relevant information on a topic from the available research literature. Literature searches range from short fact-finding missions to comprehensive and lengthy funded systematic reviews. Or, you may want to establish through a literature review that no one has already done the research you are conducting. If so, a comprehensive search is essential to be sure that this is true.
Whatever the scale, the aim of literature searches is to gain knowledge and aid decision-making. They are embedded in the scientific discovery process. Literature searching is a vital component of what is called "evidence-based practice", where decisions are based on the best available evidence.
Research literature writes up research that has been done in order to share it with others around the world. Far more people can read a research article than could ever visit a particular lab, so the article is the vehicle for disseminating the research. A research article describes in detail the research that's been done, and what the researchers think can be concluded from it.
It is important, in literature searching, that you search for research literature. Scientific information is published in different formats for different purposes: in textbooks to teach students; in opinion pieces, sometimes called editorials or commentaries, to persuade peers; in review articles to survey the state of knowledge. An abundance of other literature is available online, but not actually published (by an academic publisher)--this includes things like conference proceedings, working papers, reports and preprints. This type of material is called grey (or gray) literature.
Most of the time what you are looking for for your literature review is research literature (and not opinion pieces, grey literature, or textbook material) that has been published in scholarly peer reviewed journals.
As expertise builds, using a greater diversity of literature becomes more appropriate. For instance, advanced students might use conference proceedings in a literature review to map the direction of new and forthcoming research. The most advanced literature reviews, systematic reviews, need to try to track down unpublished studies to be comprehensive, and a great challenge can be locating not only relevant grey literature, but studies that have been conducted but not published anywhere. If in doubt, always check with a teacher or supervisor about what type of literature you should be including in your search.
By undertaking regular literature searches in your area of expertise, or undertaking complex literature reviews, you are: