Unfortunately the answer given is unclear, and I believe inaccurate. I’ll try to clarify based on what I know about Webinars.
Answer given was:
Attendee - The(sic) person who has attended the meeting.
Registrant - The(sic) person who has registered the meeting.
A registrant is a person who has “requested” or “registered” an intent to attend a meeting. Registrants can be automatically allowed, or manually allowed/denied via the API and the Web UI (and meeting configuration).
A registrant who is “allowed” is an attendee and will have a unique link to join the meeting/webinar. Accepted registrants can be automatically sent email reminders with a unique attendance link. After a meeting has ended, Attendees include those who actually attended, and those who missed the meeting. Emails can be sent separately to these two categories.
It’s actually more complicated than that, however, as there is also the notion of " Users" (https://support.zoom.us/hc/en-us/articles/203028489-Auto-Registration) and I don’t understand the distinctions. Users have passwords.