Neither. Over the Thanksgiving week, selected Midshipmen and Cadets who meet academic and leadership standards are given a few days extra leave to give presentations, meet and greet candidates, talk to parents and prospective high school students, and in general get the good word out about the Academies and their opportunities. All the Academies have found that a real, live, walking, talking Midshipman/Cadet is the best ambassador and recruiter that you can have and they make use of that during this time. BGOs, ALOs, and FFRs usually help in the setting up of the event under the sponsorship of the MOCs.
You probably have gotten an invitation due to the fact you are on the MOC interview list. There will probably be a lot other attendees from other sources. There is not a requirement to attend but considering the fact you can talk to a Mid/Cadet about the Academy and the fact there will probably be someone from the MOC's staff observing, you would be very wise to attend.