Dear Gentlemen, I will try to answer your question in a very easy way. First you have to note the following. 1) On all aircraft there is something called SHOCK STRUT that is functioning as shock absorber.2)The shock absorber has mechanical arrangement inside it. 3)Basically, the mechanical arrangements are AIR (NITROGEN) and OIL (SPECIFIC TYPE).4) Please imagine with me something like cylinder . From inside think as if there is a plate dividing this cylinder into two chambers one that is filled with oil another pressurized with air. The plate that divides the cylinder has a hole in the middle. When the aircraft land, the oil will be compressed in the lower chamber and try to pass this hole in the plate and enter the air pressurized chamber (the upper chamber). This mechanism is absorbing the shock of the landing. Please note that I am trying to facilitate the idea but ofcourse its somehow more complicated than this but basically its in this way. Now you must know something, during landing of the aircraft the oil in the shock strut absorb more of the shock. While during aircraft taxi at the airport, the air is absorbing the shocks or load of the aircraft. i hope this can help you understanding the idea. Regards.
Aircraft Maintenance Engineer / Ayman Shak'ah.