Secondary Sources: Materials that place primary sources in a 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 now 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.