CONNECT ID is dealing with identity management, or more specifically authentication, authorization, and CONNECT user data.
Authentication and authorization
CONNECT ID contains an authorization server which supplies functionality for user signup/registration, user login, and getting authorization to access a user's protected resources, like email address, phone number, payment functionality, etc. The result of sending an authentication/authorization request to the authorization server is among other things an OAuth access token. The OAuth access token can be used to get access to a user's protected resources that they have authorized the client should get access to. See CONNECT ID authentication and authorization for details.
CONNECT ID also contains a set of APIs for accessing and managing the user data that has been stored on the user in CONNECT, with operations such as get/update basic user data and get/add/remove email addresses and phone numbers. Some of these API endpoints can be accessed from an OAuth client using an OAuth access token, while some may only be accessed using HTTP Basic authentication from a server. See CONNECT ID user data for details.