An encyclopedia or dictionary entry will help introduce you to a topic by providing a brief description and some context.
A book is a good place to get a broad overview of your topic, with individual chapters that cover different sub-topics.
A newspaper or magazine article is useful when researching current events, as they are published within short timeframes and written for popular audiences in plain language.
A journal article allows you to dig deeper into your topic, as they are usually narrowly focused and written by experts in the field. Be cautious, as many journal articles use dense, technical language.
