In general, there are three types of resources or sources of information: primary, secondary, and tertiary. It is important to understand these types and to know what type is appropriate for your coursework prior to searching for information.
Sometimes sources can be a blend of types. A dissertation may contain original research (primary source) as well as analysis of that research (secondary source). An encyclopedia entry may act as a tertiary source but the information may be referenced as a secondary source. Newspaper articles written at the time of a major event are primary sources; newspaper articles that provide additional information and analysis after the event can act as secondary sources.
Understanding how to read a citations and references can help make your research time more efficient. The resources below can help.