Page 8. " I will not tolerate mention of your abnormality under this roof "

In J.K. Rowling’s world, witches and wizards live alongside non-magical people in a ‘normal’ way, although they have a separate world unknown to Muggles. Unlike his aunt and uncle, Harry Potter was born with magical powers and his unusual abilities scare Mr Dursley and his family. That is the reason why magic is banned from being mentioned in the house.

Harry's mother, Lily, was born in a Muggle family and she discovered that she was a witch when, at age eleven, Hogwarts sent for her. At the school she met Harry's father, James Potter, and after they got married, she totally abandoned her Muggle life. Her sister, Mrs Dursley, never approved of Lily's choice so she always tried to keep her distance from the Potter family. When Harry's parents were killed by Voldemort, the Dursleys were obliged to care for the boy since he had no other family.

Page 16. " Dobby is a house-elf "

Elves are magical creatures, originally found in German mythology.  They can be benevolent or malicious (sometimes called "light" and "dark"), and have various magical powers.

The Elves and the Shoemaker by the Brothers Grimm

In The Lord of the Rings, J.R.R. Tolkien conjures an entire race of elves who rule nobly and support the hobbits in their quest.

J.K. Rowling has subverted this tradition, by turning elves into domestic slaves: "house-elves". 

         

Page 18. " Albus Dumbledore is the greatest Headmaster Hogwarts has ever had "

The naming of Professor Albus Percival Wulfric Brian Dumbledore is thought to have been inspired by Rowling’s school headmaster, Alfred Dunn. Others believe that his four names represent the British Isles: Albus (a masculine form for Alba, Scotland’s ancient name), Percival (a Welsh knight mentioned in the Arthurian tales), Wulfric (a name found in the Anglo-Saxon legends thus representing England) and Brian (there was an Irish high-king called Brian Boru).

Dumbledore is an 18th century English term meaning bumblebee.