How OpenID Connect Works - Glossary

The OpenID Connect protocol, in abstract, follows these steps:

End user navigates to a website or web application via a browser.
End user clicks sign-in and types their username and password.
The RP (Client) sends a request to the OpenID Provider (OP).
The OP authenticates the User and obtains authorization.
The OP responds with an Identity Token and usually an Access Token.
The RP can send a request with the Access Token to the User device.
The UserInfo Endpoint returns Claims about the End-User.

Terminology

Authentication

The secure process of establishing and communicating that the person operating an application or browser is who they claim to be.

Client

A client is a piece of software that requests tokens either for authenticating a user or for accessing a resource (also often called a relying party or RP). A client must be registered with the OP. Clients can be web applications, native mobile and desktop applications, etc.

Relying Party (RP)

RP stands for Relying Party, an application or website that outsources its user authentication function to an IDP.

OpenID Provider (OP) or Identity Provider (IDP)

An OpenID Provider (OP) is an entity that has implemented the OpenID Connect and OAuth 2.0 protocols, OP’s can sometimes be referred to by the role it plays, such as: a security token service, an identity provider (IDP), or an authorization server.

Identity Token

An identity token represents the outcome of an authentication process. It contains at a bare minimum an identifier for the user (called the sub aka subject claim) and information about how and when the user authenticated. It can contain additional identity data.

User

A user is a person that is using a registered client to access resources.