According to CrossRef, a DOI (digital object identifier) is a "unique alphanumeric string assigned to a digital object, such as an electronic journal, article, report, or thesis. Each DOI name is unique and serves as a stable, persistent link to the full-text of an electronic item on the Internet".
The Chicago Manual of Style prefers the use of DOI for access points to digital resources. If no DOI is assigned and the reference was retrieved online, a URL or other digital identifier may be provided.
DOIs may be given in different formats in the source, but should be presented as above in your notes & bibliography.
If you ONLY have the DOI and need to find article information, use the following link :
From there, you can type or paste the DOI in the search box. The search will (in most cases) lead you to the publisher's website.