it would take me a LONG time to fully explain the story, but i actually did some research regarding the plot as well. basically, cloud and co. attempt to save the world from shinra corp who is slowly destroying the world by sucking the life force out of the earth. cloud's old 'hero', sephiroth shows up, however, and beats them to the punch by killing pres. shinra. sephiroth then concocts a plan to bring back his mother JENOVA who had been originally sent to kill the ancients as well as the world (basically ancients = protectors of earth, JENOVA = destroyer) as well as become a god by absorbing the life force from the earth. to do this, he has to make a huge scar in the planet so that the lifestream would be concentrated in one area. therefore, he summons meteor. aeris, however, being a descendant of the ancients, summons holy, which is supposed to then counter meteor and save the world. in the end, after cloud and co. kill sephiroth (who you find out was dead all along; cloud killed him years before. the sephiroth you see during the game is actually a figment of his willpower), meteor begins to hit midgar, but holy, instead of destroying it, actually aids meteor. however, the lifestream begins to come out of the earth and then the screen goes black. you then see nanaki (red xiii) with children 500 years later, looking at the destroyed midgar. (but still living earth)
phew that took awhile. but that was about as well as i could sum it up without taking hours
