The moderator's job is to help the audience get their needs met through a panel format. The moderator sets the tone, the pace, and control of the content, staying ever-vigilant in keeping it relevant for the audience. It is the moderator's responsibility to make sure the panel is lively, engaging, and worthwhile.
A panel discussion is a specific format used in a meeting, conference, or convention. It is a live, in-person or virtual discussion about a specific topic amongst a selected group of panelists who share differing perspectives in front of a large audience.