Reviewing literature, the end product of which is often a written document known as a literature review, is an essential part of research. This is where you read around your research topic, using both primary and secondary sources. The aim of a literature review is to understand the background theory and to find all of the important research (or the vast majority at least!) that has been conducted on your topic.
Reviewing literature can help also you develop your research question. For example if you had chosen a research topic of pine weevil (Hylobius abietis) control in a forestry situation, you could be struggling to develop a research question. After a thorough review of the literature, however, you identify several areas for original research, such as investigating the impact of entomopathogenic nematodes.