WBS Stands for Work Breakdown structure. As It, itself suggest that a major task is divided in to further parts or you can say again Wbs-Element.and so on .So that , we can handle a major project properly Wheather it is related to cost planning , Time planning , Available Resources.etc. Technically Wbs-element is Co-object like Internal order.
whereas Network is basically represent the flow of process or tasks within project. It is used for controlling, Analyzing, monitoring the cost time , resources with respect to particular task.
You can learn in detail from link given below:-
http://help.sap.com/saphelp_erp60_sp/helpdata/en/80/ea89395eb58c4f9d0c3e837cf0909d/frameset.htm
