Harry Potter's excellent adventure begins with the death of his parents at the hands of "He Who Must Not Be Named" AKA the evil wizard Lord Voldemort. Inexplicably, baby Harry magically defends himself against the evil wizard's attack, kills him (or so it is thought), and becomes internationally reknowned as "The Boy Who Lived," the savior of the wizarding world.
The powers that be then deemed it appropriate to hide Harry amongst "muggles," non-magic users who are unaware that wizards and witches exist, to protect him from his own fame. He lives with the Dursleys, his aunt, uncle and cousin, who mistreat him. Harry doesn't know he is a wizard until he is invited by letter to attend the Hogwarts School of Witchcraft and Wizardry shortly before his 11th birthday.
He meets Hermione Granger and Ron Weasley, his best friends in the series, on the train ride into Hogwarts.
The school is divided into four houses (think fraternities), and Harry is chosen to be in Gryffindor.
Harry, Ron, and Hermione quickly begin to suspect their potions teacher, Severus Snape, of foul play, but in the end, it's their Defense Against the Dark Arts teacher, Professor Quirrell, who's acquired the sorcerer's stone, an artifact meant for bringing Voldemort back to life.
Harry saves the day, and Gryffindor wins the house cup.