The phrase "essay editor" refers to either an application or an online service than analyzes written work and makes necessary correction with regard to spelling, grammar and plagiarism. One example of a free online editor is Paper Rater.
Paper Rater is a free online service that improves the essays submitted by students. The service prides itself as "the most powerful automated proofreading tool," which it accomplishes by employing information retrieval, data mining, computational linguistics and natural language processing. Its plagiarism detection functionality takes advantage of the indexes provided by the major search engines such as Yahoo, Bing and Google. The service can be used by pasting the text in the appropriate box and clicking the Get Report button.