Scholarly article: Written by a scholar or an expert in the field and reviewed by peers who are experts in the same area. In many databases, you can limit your search to scholarly, peer-reviewed journals. Used when you need expert evidence. 

Popular journals: Written for a general audience rather than for professionals or scholars. Examples include The New Yorker and People. Used when you need basic facts, information of current topic, or public opinion.

Primary source: An item that was created during the period you are studying. Examples include newspaper accounts, government documents, letters, diaries, autobiographies, speeches, and oral histories. Used when you need eye witness accounts. For more information about researching using primary sources, click here.

Secondary source: A source that is one step removed from an event and analyzes primary sources. Most books and articles are secondary sources.

Used when you need experct evidence, basic facts, and general overview of a topic.