If I could 'easily explain' the processes I would be working as an educator in the media, being paid large sums of money to front Earth science programs on the Discovery channel. Anything that involves details is being addressed at a serious level that has necessarily excluded 'easy explanations'. The driving force for plate tectonics is currently debated. Put differently, the role of currents, specifically convection currents in plate tectonics has been disputed. Researchers have variously argued for convection currents dragging plates around; for ridge push, where magma intruded at mid-ocean ridges push the plates apart; for slab pull, where descending slabs drags the plates after them; and slab suction, where sinking plates induce mantle currents that pull the plates. The present consensus and remaining uncertainties are summed up quite well in this 2010 paper, from which I quote "Although there is consensus that the 1- to 10- cm-per-year motion of plates is driven largely by the thermal buoyancy within subducted slabs and perturbed by upper-mantle solid-solid phase transitions and cooling of oceanic lithosphere from ridge to trench, the importance of the aseismic extension of slabs within the lower mantle remains unresolved."