If Harry Potter had not received the letter, he would have stayed with the Dursleys, unaware that he was a wizard. He would have gone to a Muggle school named Stonewall High. He would have never known the truth about his parents and would be thought that they had died in a car accident. Harry would not have defeat Voldemort, and only Merlin knows what would have happened with the wizarding world. Finally, Harry would not have met such amazing and loyal friends as Ron, Hermione, and Ginny.