What is a Digital Object Identifier (DOI) and why is it important?
A digital object identifier (DOI) is a character string (a "digital identifier") used to uniquely identify an object such as an electronic document such as an article from a magazine or journal from a library database.
It is a permanent number that is stable and makes linking to a document easier.
DOIs are better than URLs because URLs are unstable and can change often.
It is a system that started around the year 2000.
If you have an article with a DOI, you can use a DOI resolver and find the article:
To resolve a DOI name, it may be input to a DOI resolver (e.g., at www.doi.org) or may be represented as an HTTP string by preceding the DOI name by the string: http://dx.doi.org/
Many citation styles such as APA and Chicago prefer that you use a DOI instead of a URL in the bibliography or list of references.