What happens during registration of a subject, and what are the synonyms for it?

Registration creates the subject's partial identity in the organisation's context: a digital identity with attributes and roles, usually verified attributes, often an identification, and authentication means bound to the subject. Synonyms are onboarding and creating the user account.

Step by step, registration:

• Creates a partial identity in the context of the managing organisation. "Partial" (Teil-Identität) because the organisation only records the slice of the person that is relevant to it, not the whole person.
• Assigns attributes and roles to that digital identity.
• Usually verifies the attributes; attributes that are not verified count as merely self-declared.
• Often identifies the subject, meaning establishing beyond doubt which natural person this is.
• Assigns authentication means to the digital identity and binds them to the subject, so that the subject can later authenticate.

The quality of everything that follows is capped by registration: a password reset can be perfect, but if the person was never properly identified, the account still belongs to "someone who claimed to be Alice".

Go deeper:

• NIST SP 800-63A-4 Identity Proofing and Enrollment — how a registration is graded: identity assurance levels and the strength of the evidence that was checked.