In CQ5 we use these node types interchangeably but at time we need to know the intricacies of these different types of nodes.
nt:folder -: This node type represents a plain file system folder (it can have nt:folder and nt:file children and only a few restricted meta data properties) // so quite restricted in terms of properties and nodes.
sling:folder -: This node type is basically nt:folder + nt:unstructured in one, i.e. it can be used inside other nt:folders. // should be used more often.
sling:orderedFolder -: The following node type is sling:folder + an ordering scheme bundled into one. Sling ordered folders just keep the order in which nodes are inserted, the nodes won’t do any sorting by themselves