WBS in Project Management stands for "Work Breakdown Structure". This professional sounding term simply describes what should be common sense when planning a project: think about what needs to be done !
I have been reading a statement by a project manager recently saying that deliverables are more important than activities. And: beware of too much detail when planing and micro-management.
While I would agree that deliverables are more important than "how" you create those (a fundamential statement in the Agile Manifesto: "Working software over comprehensive documentation") I also would say that a project manager actually needs to worry about the "How" – at least to some extent. The art of project planning of course always is to choose the right level of detail.
A WBS itself actually focuses on the "how": that’s why it is called W ( "Work" ) Breakdown Structure. A WBS should describe the tasks and activities to accomplish something. I also agree: beware of too much detail ! But this is true as well: beware of too less detail. I simply have seen too many projects starting where almost nothing has been planned.
To describe deliverables ( and that’s probably the first thing you do in an early phase of the project planning when you identify the components to build ) a P ("Product" ) Breakdown Structure (PBS) should be used. Once you know the components you might want to go into some detail to describe the tasks needed to create those components ( deliverables ). Deliverables of course also can be features of components ( thus a level deeper in the PBS ).
PBS and WBS can be combined: you would have components and features on the higher levels and tasks defined with a reasonable amount of detail on lower levels.
If later on you have transformed your overall WBS to a gantt chart this would give you the benefit to see the progress for components and features in a high level status report.
Mindmapping by the way is a great technique to initially create a PBS and then add the WBS – hopefully with involvement of as many team members as possible.