are the same thing. It is a place on a bay, seashor, river or canal where ships can load and unload people and things. It might be built on pilings or perhaps not. Berths or moorings are located along the wharf where ships can stop or 'park.' Piers often extend from wharfs to accomodate more ships or allow them to moor during low tide etc. Jetties are typically used to channel river water or ocean currents.
Ahh the maritime trade centers. Awesome place for adventures. hmmmm.