What is the difference between floor and panel?!

[smm.144]

What is the difference between floor and panel?! I can't figure it out..

[waldemar.okapa]

Actually for calculation purpose there is no differenece between panel, floor and wall.
There used to be panels only in previous versions.

Floor and wall attributes are used to make easier selection, hierachy in the object list, unification with Revit.
There are devoted dialogs which make easier definition of vertical wall and horizontal floor.