Students may only use Turnitin at the direction of an instructor. As an instructor, you must first create a dropbox in P.L.A.T.O. that has Turnitin enabled in order for Similarity Reports to be generated.
The essays submitted by students are stored in a database used to check for matching text which helps deter one student from using another student's paper. Remember it is still up to YOU to determine if a student has plagiarized. In addition to student papers, the database contains a copy of the publicly accessible Internet, with the company using a web crawler to continually add content to Turnitin's archive. It also contains commercial and/or copyrighted pages from books, newspapers, and journals.