You should be aware of whether your Zoom session will be a Zoom Meeting or a Zoom Webinar. It might not be obvious, but look for either Meeting or Webinar (typically capitalized).
In general, Meetings are for smaller groups, usually no more the 30-50, each of whom has the ability to speak and show their camera video. As long as everyone “plays nice,” chaos and confusion can be kept at a minimum. Personally, I find that any engaged crowd over 10-15 people can really get bogged down, unless someone maintains good crowd control.
In Webinars, which can be small, but more often for 50 to “many thousands”, a select number of people are able to speak and show their camera video. These people are known as “Panelists”, in Zoom lingo, and are generally the special invitees who will be giving a presentation, sometimes one of many presentations in a longer Webinar. The other people, known as Attendees in the Zoom world, don’t generally have the ability to speak, and do not have the ability to show their camera video.
In a Zoom Meeting, you have much control over how your Zoom windows are displayed. In a Zoom Webinar, the host may fix the layout of your Zoom window, very often to the “Speaker View” which shows only the current speaker (Panelist, as Zoom calls them), along with any slides or other screen sharing.
In a Zoom Meeting, everyone is normally given access to Chat, and can generally chat individually with other participants, or with “everyone”. In a Zoom Webinar, Chat is often turned off, especially when the Attendees are potentially “random people from most anywhere”, but often left turned on for larger events where mostly people know each other. In addition to Chat, there is a Webinar-only window called Q&A, where Attendees can enter their questions for the speaker/Panelist.