School Houses
Gryffindor: Harry\'s house; named for Godric Gryffindor, a Hogwarts founder; Professor McGonagall is head of house; Gryffindors are known for being brave; colors are scarlet and gold; mascot is a lion.
Hufflepuff: Named for Helga Hufflepuff, a Hogwarts founder; Professor Sprout is head of house; Hufflepuffs are known for being loyal and hard-working; colors are yellow and black; mascot is a badger
Ravenclaw: Named for Rowena Ravenclaw, a Hogwarts founder; Professor Flitwick is head of house; Ravenclaws are known for their intelligence; colors are blue and bronze; mascot is an eagle
Slytherin: Voldemort and Malfoy\'s house; named for Salazar Slytherin, a Hogwarts founder; Professor Snape is head of house; Slytherins are known for their cunning; colors are green and silver; mascot is a serpent

Students
Major Characters
Harry Potter: Our hero
Ron Weasley: Harry\'s best friend; Gryffindor house prefect
Hermione Granger: Harry\'s other best friend; Gryffindor house prefect
Draco Malfoy: Harry\'s enemy; Slytherin house prefect
Fred Weasley: One of Ron\'s older brothers, a twin, and a DA member; co-founder of Weasleys\' Wizard Weezes joke shop
George Weasley: One of Ron\'s older brothers, a twin, and a DA member; co-founder of Weasleys\' Wizard Weezes joke shop
Ginny Weasley: Ron\'s little sister and DA member
Neville Longbottom: Harry\'s friend, fellow Gryffindor, and DA member

Members of Dumbledore\'s Army
Harry Potter: Leader and teacher
Elite Members: Ron Weasley, Hermione Granger, Ginny Weasley, Luna Lovegood, Neville Longbottom
Meeting Regulars: Hannah Abbott, Lavender Brown, Katie Bell, Susan Bones, Terry Boot, Cho Chang, Michael Corner, Colin Creevey, Dennis Creevey, Marietta Edgecombe (Cho\'s "sneaky" friend), Justin Finch-Fletchley, Seamus Finnigan, Anthony Goldstein, Angelina Johnson, Lee Jordan, Ernie Macmillan, Padma Patil, Parvati Patil, Zacharias Smith (most annoying member), Alicia Spinnet, Fred Weasley, George Weasley

Hogwarts Classes
Apparition: Teaches students about to turn 17 how to "beam" themselves from one location to another. Taught by a Ministry of Magic official.
Ancient Runes Arithmancy: Magical uses of numbers
Astronomy
Care of Magical Creatures
Charms
Defense Against the Dark Arts: How to defend against evil creatures and magic
Divination: Lessons in fortunetelling using many methods (tea leaves, crystal balls, etc.)
Herbology: Study of magical uses of plants
History of Magic
Muggle Studies
Occlumency: Defense against mind reading
Potions
Transfiguration: Turning one object into another

Examinations
OWLs: Stands for Ordinary Wizarding Levels. Taken by all students in their fifth year.
NEWTs: Stands for Nastily Exhausting Wizarding Tests. Taken by select students in their seventh year.
Grades
O is for Outstanding
E is for Exceeds Expectations
A is for Acceptable
P is for Poor
D is for Dreadful
T is for Troll

Hogwarts Professors, Past and Present
Professor Binns: History of Magic; a ghost
Albus Percival Wulfric Brian Dumbledore: Headmaster
Rubeus Hagrid: Gamekeeper, Keeper of the Keys, Care of Magical Creatures
Firenze: Divination, Year 5-6
Filius Flitwick: Charms
Gilderoy Lockhart: Defense Against the Dark Arts, Year 2
Remus Lupin: Defense Against the Dark Arts, Year 3
Minerva McGonagall: Transfiguration, Head of Gryffindor House
Alastor Moody: Defense Against the Dark Arts, Year 4, also known as "Mad-Eye," former Auror
Quirenius Quirrell: Defense Against the Dark Arts, Year 1
Dolores Jane Umbridge: Defense Against the Dark Arts, Year 5
Professor Sinistra: Astronomy
Pomona Sprout: Herbology
Horace Slughorn: Potions, Year 6
Severus Snape: Potions (Years 1-5), Defense Against the Dark Arts (Year 6), Head of Slytherin House
Sybill Trelawney: Divination
Professor Vector: Arithmancy

More Hogwarts Folks
The Bloody Baron: Slytherin\'s house ghost
Argus Filch: Caretaker
The Fat Friar: Hufflepuff\'s house ghost
Dobby: House Elf, kitchen staff Years 3-6
The Grey Lady: Ravenclaw\'s house ghost
Fat Lady: Painting at the entrance to the Gryffindor common room
Madame Hooch:Quidditch and flying master
Kreacher: House Elf, kitchen staff Year 6
Moaning Myrtle: Ghost in the girls\' bathroom
Nearly Headless Nick: Gryffindor\'s house ghost
Mrs. Norris: Filch\'s watchful cat
Peeves: Poltergeist bent on mischief (not in the films)
Irma Pince: Librarian
Poppy Pomfrey: School nurse

Strange and Magical Creatures Found at Hogwarts
Aragog: Leader of giant spiders called acromantula
Bane: Head of the centaurs in the Forbidden forest
Basilisk: A type of giant snake that turns people to stone when you look into its eyes
Boggart: A creature that takes on the appearance of one\'s worst fear
Buckbeak:Hagrid\'s hippogriff
Centaurs: A race of half-horse, half-human creatures
Cornish pixies: Tiny but destructive blue winged creatures
Crookshanks: Hermione\'s cat
Dementors: Soul-suckers who normally guard Azkaban prison
Fang: Hagrid\'s boarhound
Fawkes: Dumbledore\'s phoenix
Fluffy: A three-headed dog from Year 1
Giant Squid: Often seen in the lake on Hogwarts grounds
Hedwig: Harry\'s owl
Hippogriffs: Creatures that are half horse, half eagle
Merpeople: Inhabitants of the lake at Hogwarts
Norbert: Hagrid\'s baby dragon, Year 1
Norwegian Ridgeback: A dragon breed, faced by Harry in Year 4
Pigwidgeon: Ron\'s owl
Scabbers: Ron\'s rat, Years 1-3
Thestrals: Winged horses that pull the carriages and can only be seen by those who have seen death
Trevor: Neville\'s pet toad
Unicorn: A type of horse with a horn on its forehead
Whomping Willow: A tree that packs a punch

For more creatures, see the book Fantastic Beasts & Where to Find Them