A Digital object identifier (DOI) is a string of characters used to uniquely identify an electronic document. The document can be an article, book or other text file, as well as an image, audio or video file. A DOI can be assigned to a whole journal, an article within a journal, or even a chart within an article.You will see DOI names displayed as: DOI:10.1000/182  but more recently they are given in a URL format: http://dx.doi.org/10.1000/182

Below are a few useful links, For more in depth information, look at the DOI system pages in the adjacent box, especially the FAQs and handbook.