These two sources are available online for students, staff and faculty at Boise State University. Dictionaries provide definitions of terms and phrases, and encyclopedias summarize topical areas.
Some journal articles are literature reviews. Reviews are helpful because someone else summarizes the research in a topical area (up to a particular date), essentially doing some of your research for you, and providing some context for that research. These reviews are also rich resources for identifying key articles in a specific subject area. Articles in the Annual Review publications and the literature review chapter in PhD Dissertations also contain such review information. If you want an overview of an area, try the Synthesis Digital Library.
Authors write for a variety of purposes and audiences. Sometimes their content is more suited to a journal article or conference paper, and sometimes to a book or an encyclopedia article. Books contain more material than articles, and that additional material may contain a better overview of an area, or more context. In general, the content will be older, more descriptive, and less research-based than the content of articles. Some databases are listed below that help you identify books.