Interest Groups meet on a scheduled basis (for instance, the last Thursday of every month) and you know this in advance when you indicate on your profile that you are interested in a group. Special Activities do not have a schedule…they either happen once or a few times a year, or on a more random basis. For instance, we offer a Wine Tasting Interest Group every month, but we could schedule a Weeknight Dining Out one month, and then not schedule again for a few months. Our annual Family picnic happens only once each year.