Conference
An event with an intense schedule of talks all day long would typically be called a conference. The number of participants would probably be higher than for a workshop.
Workshop
If the focus is more on group discussions and non-scheduled collaborative work, with perhaps only one or no talk a day, the event is more likely to be called a workshop. This is the model used in most scientific programs, so the difference between a program and a workshop is really only the length of the event.
Meeting
If participants are members of a network or some other type of organization and meet regularly, the event might be called a meeting.
