A DOI is a Digital Object Identifier that is used to uniquely identify journal articles and other materials ("objects"). It often appears as part of a citation, and can be an easy way to track down an item.
A DOI is made up of numbers and letters, for example: 10.1016/j.iheduc.2015.08.004 is the DOI for the article "Students' use of Wikipedia as an academic resource: patterns of use and perceptions of usefulness" published in 2016 in the journal Internet and Higher Education.
You can use the DOI to find the article using a search engine or a DOI resolver like doi.org. For example, the above DOI has the URL https://doi.org/10.1016/j.iheduc.2015.08.004
Note that the DOI will often take you to the publishers page for the article, but if you are off campus, it will appear that you don't have access to the article. If you use our Bookmarklet to load the page through our proxy server, you'll be able to access the article, if it is part of the library subscriptions.
Unfortunately, not every article or digital object has a DOI, and not everything with a DOI is available online.