Even though many Wizarding families offered to adopt the orphaned infant, Harry was placed with the Dursleys for a particular reason. Lily Potter’s sacrificing herself to save her child created a magical shield that has safeguarded Harry from Voldemort. However, Harry must live in his mother’s blood relatives’ home to maintain the protection—that relative is Aunt Petunia. Convinced Voldemort would return, Dumbledore’s priority was to keep Harry safe. The Howler Petunia received was Dumbledore’s stern reminder that she was obligated to protect Harry.
The prophecy Voldemort sought was originally made shortly before Harry’s birth. It is why Voldemort wants to kill Harry. Voldemort, however, never knew the entire prophecy, and was trying to retrieve the stored copy to learn its contents. The prophecy is known to Dumbledore, however, because it was originally told to him. Sixteen years ago, Dumbledore interviewed Sybill Trelawny for the Divination position, meeting her at a pub in Hogsmead. Although she was descended from a gifted Seer, she herself seemed minimally talented and Dumbledore declined her the post. As he was about to leave, Trelawney fell into a trance.
Extracting a memory, Dumbledore places it in the Pensieve. Sybill Trelawney’s veiled image rises, and in a familiar harsh voice recites, "The one with the power to vanquish the Dark Lord approaches… born to those who have thrice defied him, born as the seventh month dies… and the Dark Lord will mark him as his equal, but he will have power the Dark Lord knows not… and either must die at the hand of the other for neither can live while the other survives… the one with the power to vanquish the Dark Lord will be born as the seventh month dies…"
According to Dumbledore, two boys fit the prophecy: Harry and Neville Longbottom, born days apart. Both Harry’s and Neville’s parents, who were Order of the Phoenix members, defied Voldemort three times. Voldemort probably attacked Harry because he is a half-blood like himself, and therefore considered him more dangerous than Neville, a pureblood. By deliberately choosing Harry, Voldemort “marked” him as his equal, leaving the scar on Harry’s forehead. But Voldemort was only told the prophecy’s first half. The second part predicted that the marked child would have powers that the Dark Lord could never know, and that one must die at the hand of the other, for both cannot live while the other survives. The power Harry possesses and Voldemort does not is love. It is what protected Harry from Voldemort’s killing curse while ripping the Dark Lord’s soul from his body. Dumbledore confirms that the prophecy means that either Voldemort or Harry must kill the other.
Finally, Dumbledore explains why Harry was not chosen to be a Prefect: “I must confess . . . that I rather thought . . . you had enough responsibility to be going on with.”
Harry Potter films colours - Philosopher’s Stone (1/?)