A digital object identifier (DOI) is a permanent, unique string of characters that identifies specific digital content such as an online article, dataset, image, etc.). Ideally, when a DOI is assigned (by a publisher, repository host, etc.), there is metadata and a URL which is associated with the DOI which makes the DOI 'resolvable' (point to the digital object or to a web resource that gives you more information about the digital object).
All DOI numbers begin with a 10 and contain a prefix and a suffix separated by a slash. The prefix is a unique number assigned to organizations; the suffix is assigned by the the organization.
DOIs can often be used in citations in lieu of urls.
To make the DOI resolvable, add the DOI to the end of this url:
For example, doi: