The WBS is a hierarchical listing of all the work packages. Each work package should include an estimated budget and effort (time to complete the task if one person is working on it continuously).
The Gantt chart (in its modern form which includes task dependencies) is used to create the project schedule. Each work package is now influenced by the working calendar (hours and days per week work is actually done), the assigned resources, how much of the working time each resource devotes to that work package (e.g. may work 50% on task A and 50% on task B for a period of time), any required deadlines, and the dependencies between tasks, to derive the model project timeline/schedule.
So in short the WBS is a listing of the work to be performed and is input to create a Gantt chart which is the project timeline as to when that work will be completed and who will work on the tasks.