Secondary Sources: Materials that place primary sources in context. The viewpoint is from outside the original source.
Examples: Articles in magazines/newspapers/trade publications, literary criticisms, book and movie reviews, scholarly articles evaluating original research, second-hand accounts, biographies, interpretations, descriptions, commentaries.
Think you know your stuff about primary and secondary resources? Check out this amazing tutorial from Ithaca College Library. It's tough (Neil deGrasse Tyson-type questions)...but fun! And, you'll really learn a lot about how, when it comes to identifying sources, it's all about context!