OpenID is an open, decentralized, and secure way to authenticate and transfer user data across multiple websites and services. It provides a single sign-on (SSO) experience for users, allowing them to sign into multiple websites and services with just one account. OpenID is a protocol for digital identity that enables users to use one digital identity across the web. OpenID eliminates the need for users to create and manage multiple usernames and passwords. It also helps protect users from identity theft. OpenID is based on a set of standards and protocols that allow websites to securely authenticate and transfer user data. OpenID provides users with a secure and private way to access their data on multiple websites and services. By using OpenID, users don't have to give up their personal data or share their passwords with third-party sites. OpenID also provides an extra layer of security by allowing users to authenticate their identity using a trusted third-party provider.
Notice discontinued on the official site: "persona is no longer actively developed by Mozilla. Mozilla is committed to operational and security support of persona.org services until November 30, 2016. On November 30, 2016, Mozilla will shut down the persona.org services. Persona.org and related domains will be taken offline." See https://developer.mozilla.org/en-US/Persona