Overlanding beyond borders and boundaries is what the nature has put in humans by default but not everyone is quiet capable to experience it because of the tough process and not measurable awards, the awards that can not be quantified like by end you will be more aware of the history of humans around the globe in relation with the wild life, the heritage and culture that we once used to possess. The Sight and scenery of the world as a whole be captured and to be remembered for rest of your life, infact enough for you to pass time in your old age thinking of this experience.
It mainly is the self-dependant journey converted to adventure to remote or far away places. It should be done without flying. So, hard and long way to go and usually camping is the main housing for night spending where it falls. We can hardly define anytime for this it may last for weeks to years on roads and sea, where the only boundary involved is planet earth.
So, the difference between the Expedition and the overlanding is journey with the motive and journey as a motive respectively.
This is performed usually in the groups but individual examples do exist, less often to be done by the families and more by the friends in the group.