No event can run without attendees. While you might choose to run an event and accept anyone that can come (physically or virtually), often to ensure fundraising and sponsorship, you need some sort of registration system that can contact attendees.
Please add updates from your event in reverse chronological order (newest first).
There are a number of ways to register people for events, though this might not be that important for virtual events. However, you do want a way to contact people, so at a minimum, you want a mailing list of attendees. Below are a few options: