After sweeping the Poles aside like ninepins (and seriously, the Polish Army went out against the German tanks on horseback: talk about guts), the Germans settle in and promptly begin deporting all of the country's Jews into ghettos in the cities. Their homes, businesses, and belongings are confiscated. They have no means of support. They're forced to wear armbands identifying them as Jews, just in case anyone would confuse them with human beings.
Well, it's good for Oskar Schindler.
Businessman, Nazi spy, and all-around charmer, Schindler (Liam Neeson) sees a golden opportunity in this situation. After carousing with the local Nazi big shots at a city nightclub, they allow him to take over a confiscated Jewish business—an enamelware factory—using the Jews as slave labor. By producing pots and pans as mess kits for the German army, he's sure he'll make a fortune.
The business does very well. He keeps the bribes flowing to his Nazi contacts so they'll keep putting in orders for his products. It's a great deal for him, but a pretty bad one for his Jewish workers. They don't get paid—only a few surplus pots to trade on the black market. It keeps them off the cattle cars for now, but they're still living with starvation and disease in the Krakow ghetto.
It gets worse. A lot worse.
There's a new sheriff in town. Kommandant Amon Goeth (Ralph Fiennes) in Krakow supervises the construction of the new Plaszow concentration camp outside Krakow. When it's built, the Nazis empty the ghetto and herd the Jews into the camp. Those who aren't quite down with the program get shot. People unfit to work are loaded onto cattle cars in trains bound for Hell, a.k.a. Auschwitz.
His workers suddenly gone and his factory empty, Schindler's all over it like it's Taken 4: Everybody. He storms into the camp demanding that "his" Jews be returned so he can keep making money. He cajoles, bribes, and threatens in order to get them back.
Oskar continues to work both sides, keeping his workers out of Plaszow while socializing with the Nazis and greasing the wheels of his bribery machine to keep business coming.
Meanwhile, Herr Kommandant Goeth, a sadistic psychopath, enjoys using Jews in his camp for target practice. He randomly shoots prisoners from his balcony just so no one gets the idea that you can count on being alive from one minute to the next.
Schindler sees all that's going on. He's horrified. As the war goes on, he slowly stops focusing on making bundles of cash and starts trying to save the Jews in his factory. Considering how happy the Nazi regime is with his work, he's uniquely positioned to do it. He continues to pal around with Goeth and his sadistic Nazi buddies to make sure he's got the clout to keep his workers out of Plaszow.
Everything changes when Goeth receives orders to liquidate the camp and send the Jews to Auschwitz to be killed. Schindler spends the remainder of his personal fortune to save more than 1,100 of his Jewish workers from deportation—written on the "list" of the film's title. Things don't go quite as smoothly as he'd like—the Jewish women and children get sent to Auschwitz by mistake—but Schindler's con artist hustle (and a big fat bribe for the Auschwitz kommandant) manages to keep them alive until the end of the war.
Even more awesome, he turns his factory into a model of inefficiency, so there's fewer shells for the German army to lob at the advancing allies. He even manages to let his workers reclaim some of their religious traditions by observing the Sabbath on Friday nights. At the end of the war, he's broke and wanted as a war criminal, but the men, women, and children on his list are alive.
His grateful workers present him with a gold ring inscribed with a passage from the Talmud: "Whoever saves one life saves the world entire." They give him a letter to present to the Soviet Army if he's caught, attesting to his heroic actions on their behalf.
For the record, the real-life Schindler eluded the Russians and made it all the way to the American forces with the help of several of his Jewish workers. He was unsuccessful in business after the war, and was supported by donations from the Jewish community until his death. We never see this in the movie, but it's worth noting. They never forgot him.
A narrative text at the end of the film states that there are 6,000 descendants of Schindler's Jews, and only 4,000 Jews in Poland. The late great film critic Roger Ebert writes that "The obvious lesson would seem to be that Schindler did more than a whole nation to spare its Jews. That would be too simple. The film's message is that one man did something, while in the face of the Holocaust others were paralyzed." (Source)
The film closes with real survivors, walking with the actors who played them, to lay stones (a sign of love and respect) at Oskar Schindler's grave in Israel.
And now you know why.