When a conference consists of multiple sub-events which all members are expected to attend together, these are often called plenary sessions. So a Festival of Apples could have several plenary sessions one after the other on topics such as Recent Developments in Peeling Techniques, Orchard Management for Dummies, The Future of the Granny Smith, Red or Green for Pies and so on.
Events other than these such as Apple Picking and Cider Making may be called Fringe Events - they are not essential parts of the main conference and not everyone is expected to attend.
Another type of event is the Breakout Session. Generally these take place on various subjects simultaneously and people are expected to go to one or another of them depending on their particular interests or expertise. There might be one on Choosing Manure which apple growers might attend while simultaneously another session took place on Selecting Pastry which apple pie makers attended.
A less-used alternative to Plenary Session is Core Session, which might be particularly apt for an Apple Conference.