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Journal databases are collections of journals, articles, conference papers, reports, and more, generally arranged by subject. Some will only list abstracts of their collection – ie, they will tell you about the item, but you have to find it somewhere else, and some will hold the item itself.
Journal databases are:
Are the best source of academic or scholarly information for your assessments
help you locate peer reviewed articles
Are subject specific, so that you get more relevant results
Have many options for refining results, and link between themselves, so that an abstract found in one database can help you find the full text if it is held elsewhere.