Satine is a dancer at the Moulin Rouge, who is know as the legandary "Sparkling Diamond".
She has, and eventually dies of, "consumption", otherwise known as tuberculosis. She died in the arms of her lover, Christian.
The first time Christian saw Satine, she was singing "Diamonds Are A Girls Best Friend". She mistook Christian for the Duke. Zidler had said that he was marked by a waving hanky. Satine turned around at the same moment that Toualouse turned around to get a hanky from Chrisitian and therefore thinking he was the Duke she was looking for. Her life-long dream was to become an actress which wasn't quite what she was accomplishing by being a courtesan, the Duke could give her this dream. During the dance between her and Christian (still unaware Christian wasn't the Duke), Christian said that he would like to show her his poetry, but, Satine mistook this for a sexual code.
As she left, very much the same way she entered, she sang "Diamonds Are A Girls Best Friend, Reprise", she collapsed (giving us a mild hint of an illness), and one of the Moulin Rouge dancers, Chacala, caught her. Zidler gestured to him to remove her from the room. When he did, Marie and a Doctor gave her an inspection. When she awoke, she was told by Zidler how well she did. They jumped up and down like little kids. She entered the "Elphant" (satines private quarters) where Christian was and they talked about poetry, Christian saying it was "quite long and he wanted her to be comfortable". He also said he needed inspiartion. Satine stood, still believing this was a code for sex, walked over to him and initiated it, saying "does this inspire you?" She then threw him on the bed and said that he was a "big boy". He rejected the actions and moved away from the bed, making Satine roll around on the ground, until Christian started to sing, she was distracted.
When he finished, she said that "she was in love with a Duke. A handsome, loving Duke." Only to be rudely awaken when Christian tells her he is not a Duke. Satine freaks out, runs to the door, where Zidler is talking to the Duke, she slams the door closed, excaliming "THE DUKE!" and telling Christian to hide.
She started saying odd things to the Duke, mainly, "It's a little bit funny, this feeling inside." After clever thinking, Satine sent the Duke away saying that they should wait until opening night. She turned around to face Christian and telling him "Do you know how much..." But then, she fainted and Christian caught her. The Duke walked back in on them saying, as he entered, that he forgot his hat. Satine, Zidler, Christian, Satie, Toualouse, Argintianean, and and an unknown character sang "Spectaculare" to get him to believe that they were only rehursing and not doing anything suspicious.
As Christian and Satine's affection grew they had to hide their love from the Duke, because, the Duke held the rights to the Moulin Rouge. When the Duke finds out about Christian and Satine, he says that he will have Christian killed and Satine finds out she is dying of tuberculosis. Because she didn't want Christian to get hurt, she left him.
After the finale "Come What May", Satine dies in Christians arms after this long battle. The over side of the curtain is revealed and the duke storms out unaware that Satine has died.
One year later and Christian is completely depressed and alone. He ends the film by simply typing 'the greatest thing you'll ever learn is just to love, and be loved in return. The End.' The film ends with nature boy. This film leaves a very strong mark on viewers and entices you into this profound and tragic tail of truth, beauty, freedom and love.