Use background information as a starting place for understanding a topic. Search encyclopedias, government websites, NGO websites to learn the vocabulary used to describe your topics and develop keywords.
In the field of biology, primary literature is the publication of information that is original research. In other words, this is the first (or primary) place this information is available to readers. In the sciences, peer-reviewed original research is of special interest because of the rigorous standards that accepted articles must meet in order to be published.
Examples or other terms for primary literature include: scientific paper, research article, journal article, scholarly article, book, monograph (essentially a long journal article), dissertation or thesis, proceedings (published record of a conference), government document, report, notebook, journal, photograph, or database.
Secondary literature is an important part of the research process of a topic. Secondary literature is any form of literature the condenses, synthesizes, or draws upon primary literature. These sources provide a starting place for understanding a topic because they are easy to read and provide background information and they may be useful in pulling out keywords, phrases, or concepts. When using secondary sources it is important to know that is that they are not peer-reviewed and they include a second layer of interpretation of original data that may or may not be correct.
Example include books, review articles, magazine and newspaper articles, handbooks, and factsheets.