@BonaParte cv,
Peak oil, in a basic sense is the concept of the peak of production of all the oil fields in the world. Take any given oil field, it has only so much oil, once it hits a peak it is very difficult to get the remaining oil from that field, which leads to more cost in infrastructure. The reason being is that oil will not come out as easy from the ground when there is less of it packed into it. Once an oil field becomes low it takes longer to extract the little amount of oil left, also leading to more costs in production. Since American economy relies on cheap oil as of now, and once oil production starts to fall(in short being unable to comply with demand) the economy will take a hit, and in a big way that the world hasn't seen prior.
Food shortages are also a big part of the oil picture here. Due to oil, we've seen a massive population boom over the last century. Oil powers the machinery for farmers to grow crops on a massive scale. Without oil to power the machinery, serious questions on whether food can be produced come into play.
Peak oil will probably be the event everyone's lives change in a way I cannot even start to fathom. Oil is the most precious resource in the world, it's non-renewable, and the advances in science and military strength of United States is all related to oil. You can't fight a war without oil.
Lots of things will change. Countries will be vying for energy resources that are quickly depleting, that means wars, oppression, famine, death. The concept of the world population going down is a big point of discussion in reference to peak oil.
Oil is THE driving force in US foreign policy. Oil companies hold such influence that they have drived us to war many times and have affected the geopolitical structure of many countries. One cannot have a true understanding of world events without admitting the fact that oil is rapidly being depleted.