What are means by WBS ( work breakdown structure)?

Work Breakdown structure is the smallest delivrable task which be done and can be managed , And it is the best and right way to plan any project , (take into consideration -complex projects will need a great effort to reach the right WBS ) and the WBS shows how much you are leading the project plan and it muct be done with a complete team not just one PM . because it includes all technical details of the way the project needed to be accomplished and completed.

Work Break Down structure is an organised approach by which the primary goal is broken down into sub divisions, which may include work packages, phases and deliverables. 

A project or goal is usually achieved by performing a number of smaller tasks. WBS starts with the ultimate goal. The immediate tasks that are to be performed to establish the goal comes on the second level of WBS. Below this level comes the sub-tasks that are to be performed to achieve the second level tasks. Continuing in this way, a hierarchical structure is obtained. Thus the hectic task of establishing a goal is converted into many simple tasks. The project manager can concentrate on these simple tasks and do the necessary arrangements to carry out each tasks effectively which in turn results in the successful completion of the project.