Before I go into more detail on her story you may want to read up on Jack Sparrow at Wikipedia.
There is alot of info not mentioned in the movies. (Well the frist two at lest) I'm not sure if it will be in the 3rd. So there may be spoilers there for I shall use a lj-cut.
Her mother was a female pirate that Jack came across well he was a merchant sailor working under Beckett for the East India Trading Company. Jack and his crew took the pirate ship Eve was on. And Eve then joined Jack's crew. The two developed a love/hate relationship and thus Pearl was born. She was born at sea abroad the Wicked Wench. And lived with her parents for 3 years until Jack refuses to transport slaves and instead frees them in Africa. Beckett sanctions the torching (and sinking) of the Wicked Wench, and literally brands Jack Sparrow a pirate. I say Beckett hangs Eve and takes Pearl to raise as his own daughter.
But Jack had given Pearl a necklace of a Sparrow holding a Pearl. And only he can remove it. So there for she always has it. At the age of 16 Pearl presses Beckett about him not being her real father. After alot of pressing she learns he is in deal not her real father. So she sets out looking for the man who is her real father.
She looks just like Jack Sparrow. She has long black hair. Dark brown eyes. When not froced to wear the tight dresses of the stuffy life Beckett riased her into she likes to wear 'boy' clothes. Plan shirts, pants and boots.
AIM Screen name: Pearl Sparr0w.