TurnItIn is a grading and feedback tool used at Nexford University to provide you with fast and relevant feedback from faculty.
As part of this, TurnItIn runs originality and plagiarism checks on your submissions to check your writing for citation mistakes or inappropriate copying. When you submit your assignment, TurnItIn compares it to text in its massive database of student work, websites, books, articles, etc.
If you have any questions about how to use TurnItIn, check out their Student Resource Hub.