What is the difference between the AID and the VIT of the associations?

The AID are the general introduction days of Wageningen organised by Wageningen University, during which you'll get acquainted with your fellow students, the student life, the (student) associations and the city. The VIT of the student associations is the association introduction time in which you participate to get to know the association. The VIT is compulsory if you want to become a member of the association.