A wing fence , as T P mentioned reduces spanwise flow therefore reducing the strength of wing tip vortices. It overall increases wing efficiency as the vortices are the main source of induced drag.
Winglets increase the aspect ratio of the wing without increasing its span. As you probably know wings with higher aspect ratio tend to have lower induced drag.
It is not always necessary or benefitial to employ winglets as other considerations must be taken into account such as weight and costs.
Sometimes you get very little benefit in performance, depending on profile of the wing etc. This is probably the case with airbus.
Also in some cases it is possible to getforward force component aiding your flight.