Turnitin checks student work against the work of others; from other student submissions ( at our school and other schools or educational institutions), the web and online journals.
Each time an assignment is submitted to Turnitin a Originality Report is produced which may show text that can be found elsewhere. This does not mean that the assignment is plagiarised as Turnitin may also find material in the submission which has been quoted and referenced.
As well as detecting plagiarism in assignment work, Turnitin helps develop writing skills by encouraging paraphrasing, summarising and correct citation.
Turnitin's Instructor Guides detail how you can use Turnitin's Canvas Plagiarism Framework in your classroom.