"Literary criticism is the evaluation, analysis, description, or interpretation of literary works. There are many types of literary criticism: some examples include historical criticism (understanding of the time period in which the novel is set) and biographical criticism (explains how the novel is based on the life of the author along with events that mirror Fitzgerald's life). Character studies involve the in-depth analysis of the characters in the novel. Please note that Literary criticism is NOT necessarily negative---criticism involves looking at both the positive and negative qualities."
(Sources: Internet Public Library & St. Mark's School of Texas)
"Literary criticism can be published as journal articles or full-length books. In general, it is the peer-reviewed work of scholars who discuss a particular text or texts, including fiction, poetry, plays, films, and other works. A work of literary criticism differs from a book review in that it is typically a more in-depth critique of a work, and it's most often intended for an academic audience."
(excerpt from LibGuides CCSU, http://libguides.ccsu.edu/content.php?pid=59706&sid=438732)
When searching a database, use the title of the work and/or author's name, and a theme as your keywords
ex. The Great Gatsby American Dream
BE AWARE....you may run into TONS of Spark Note-like sites. Use search term+site.edu for premium results!
Keep in mind that your teacher can quickly form an opinion about your work based on the sources you used.