Classroom view
Classroom view is a special view because when you move cards in this view, then only the classrooms are changed. The positions of the cards are not changed.
So for example the following picture shows you that you can easily move physical education for 8H from Small to Big gym room:
The cards shown in the control panel are either cards that are not yet placed in the timetable or cards that are placed but they do not have a classroom assigned yet. These are marked with white stripe: