Hogwarts

Gryffindor
Harry Potter is the main character, "the boy who lived."
Ron Weasley is Harry's best friend, from a large and poor wizarding family.
Hermione Granger is the smartest in her year, an excellent magician, and very persistent. Neville Longbottom seems awkward at first, but by the end of the story he reveals himself to be a true brave man.
Ginny Weasley is Ron's younger sister, a bright and powerful witch.
Fred and George Weasley are twin brothers, pranksters and inventors, always pulling pranks. Slytherin
Draco Malfoy is the son of Lucius and Narcissa Malfoy, initially arrogant and haughty, but the story also shows his vulnerable side.
Pansy Parkinson often acts as Draco's loyal ally and enjoys teasing students from other houses. Blaise Zabini is calm and calculating, keeping a bit out of the fuss.
Theodore Nott is another Slytherin student, quite withdrawn.
(Even earlier, Tom Riddle (the future Voldemort) and Severus Snape studied in Slytherin - but they were already graduates of previous years.)Ravenclaw
Luna Lovegood is unusual, dreamy, sees what others don't notice; many people initially consider her strange, but then appreciate her sincerity.
Cho Chang was a talented witch and Seeker for the Ravenclaw Quidditch team; Harry had a crush on her. Hufflepuff
Cedric Diggory is a very decent and honest guy, captain of the Quidditch team and one of the champions of the Triwizard Tournament.
Hannah Abbott is an active student who later becomes Head of House.

Minerva McGonagall – Transfiguration. This is about turning one thing into another (for example, a match into a needle).
Severus Snape (before book 6) and Horace Slughorn (from book 6) teach Potions. They brew a variety of potions here, from the simplest to the most complex, like Felix Felicis. Filius Flitwick teaches spells. This is where they teach you how to wave your wand and pronounce the words needed to cast the desired magic. Quirinus Quirrell (book 1), Remus Lupin (book 3), and then a few more teachers teach Defense Against the Dark Arts. The most unstable subject: there's a new teacher almost every year, and the lessons focus on how to defend yourself against Dark Magic, Boggarts, werewolves, and more. Pomona Sprout teaches Herbology. It's not just botany, but magical plants: how to grow them, harvest them, and how to defend yourself if one suddenly decides to strangle you (like Devil's Snare).
Cuthbert Binns is a history of magic. Led by a ghost, it tells stories of important events in the wizarding world. Aurora Sinistra is an astronomy workshop. Here, people look through a telescope, memorize the stars, and map the sky.
Rubeus Hagrid – Care of Magical Creatures. Students meet a variety of creatures, from the cute to the downright dangerous. Sybil Trelawney – Divination. Fortune telling, predictions, reading tea leaves – basically, everything about trying to see the future.
Madam Hooch: Broomstick Flying. This class is only offered to first-year students: they learn broomstick skills and the basics, and then they train for Quidditch.

First year
Second year
Third year
Fourth year
Fifth year
Sixth year (this is where Draco goes through some tough times)
Seventh year (final, with ZHABA exams)

Gryffindor (founder - Godric Gryffindor; qualities: courage, nobility).
Slytherin (founder - Salazar Slytherin; qualities: ambition, cunning).
Ravenclaw (founder - Candida Ravenclaw; qualities: intelligence, creativity). Hufflepuff (founder - Penelope Hufflepuff; qualities: hard work, loyalty).