TurnitinUK is an online service which compares student assignments with online sources including web pages, databases of reference material, and content previously submitted by other users across the UK.
The software makes no decision as to whether plagiarism has occurred; it is simply a tool which highlights sections of text that have been found in other sources. The assignment which has been submitted to TurnitinUK and an Originality Report (the report which identifies the text matches found) are displayed for the member of staff to view. The member of staff can see whether resources have been appropriately referenced and hence whether plagiarism has occurred.
The Student Instructions for TurnitinUK show you how to submit an assignment to TurnitinUK through MyAberdeen.