Main Groups:
* Gryffindor: Known for bravery, chivalry, and determination. Harry, Ron, Hermione, and Neville belong to this house.
* Hufflepuff: Values hard work, dedication, patience, and loyalty.
* Ravenclaw: Focuses on intelligence, wit, creativity, and learning.
* Slytherin: Associated with ambition, cunning, leadership, and resourcefulness. This is the house of Draco Malfoy and Severus Snape.
Other Groups:
* Dumbledore's Army (DA): A secret organization of students formed by Harry to learn Defense Against the Dark Arts.
* Order of the Phoenix: A secret society fighting against Voldemort. Members include Harry, Ron, Hermione, Sirius Black, and Remus Lupin.
* Death Eaters: Voldemort's followers. They are dark wizards who use dark magic and terror to achieve their goals.
* The Ministry of Magic: The governing body of the wizarding world. It handles various aspects like law enforcement, education, and international relations.
Important Note: These are just some of the main groups. Within the Harry Potter universe, there are various other organizations, clubs, and societies that are mentioned, each with its own purpose and members.