This article has been superseded by the new information site at https://info.orcid.org/documentation/integration-and-api-faq/
API stands for Application Programming Interface; it specifies how programs can interact with each other. The ORCID API specifies how an outside program can interact with the ORCID Registry to retrieve and update data in the Registry.
OAuth is an open standard for authorization between computer systems. Through OAuth, ORCID researchers share access to their ORCID record with another program. Learn more about OAuth on our Member Support Center: Introduction to OAuth.
If you are new to APIs and OAuth we suggest attending one of our ORCID webinars to get an introduction to the technology ORCID uses.