"Or yet in wise old Ravenclaw,
If you've a ready mind,
Where those of wit and learning,
Will always find their kind."
—The Sorting Hat[src]

Ravenclaw is one of the four Houses of Hogwarts School of Witchcraft and Wizardry, founded by Rowena Ravenclaw. Members of this house are characterised by their wit, intelligence, creativity, and wisdom. Its house colours are blue and bronze, and its symbol is the eagle. The house ghost, who in life was the daughter of the house's founder Rowena Ravenclaw, is the Grey Lady. Many great wizards and witches have come from this house, including Filius Flitwick and Luna Lovegood.
Ravenclaw roughly corresponds with the element of air.


Common Room
Luna: "What do you think, Harry?"
Harry: "What? Isn't there a password? What if you get it wrong?"
Luna: "Well, you have to wait for somebody who gets it right. That way you learn, you see?"
— Luna Lovegood and Harry Potter entering the Ravenclaw common room[src]


The Ravenclaw common room is in one of the castle's towers and is wide and circular. You have to climb a tight spiral staircase to get there. It has graceful arched windows, and the walls are hung with blue and bronze silks. The domed ceiling is painted with stars, which are echoed in the midnight-blue carpet. Tables, chairs, and bookcases cover the expanse of the floor, and a white-marble statue of Rowena Ravenclaw sits next to the door that leads to the dormitories above. Harry Potter entered the common room in 1998 while searching for clues to the location of one of Voldemort's Horcruxes.

Unlike the other common rooms in the school, a logical riddle given by a bronze eagle-shaped knocker must be answered to enter. This could prove troublesome as anyone with enough intellect could intrude into the dormitory, as is shown in Harry Potter and the Deathly Hallows where Professor McGonagall had no trouble entering by answering the riddle correctly. However, Hermione stated in her first year that most wizards and witches do not have much sense of logic, which might be something that Ravenclaw noticed herself and decided to use riddles instead of passwords.

Traits
"Wit beyond measure is man's greatest treasure."
—Rowena Ravenclaw[src]

Ravenclaw House prizes intelligence, creativity, resourcefulness, cleverness, knowledge, and wit in its members. Thus, many Ravenclaws tend to be academically motivated and talented students. Hermione Granger, an extremely intelligent witch and the top student in her year, was sorted into Gryffindor, though she admitted that the Sorting Hat had seriously considered placing her in Ravenclaw.

Ravenclaw House appears to have little rivalry with the other houses, except in Quidditch (in which case it is most fiercely competitive with Hufflepuff). Harry Potter believed that they tended to side with Gryffindor in its rivalry with Slytherin, as did Hufflepuff house. However, during the 1994 Triwizard Tournament, Ravenclaws supported Hufflepuff Champion Cedric Diggory over Harry. This may indicate that Ravenclaw tends to have a closer relationship with Hufflepuff house or simply be a result of the widespread belief that Harry had cheated in order to get his name in the Goblet of Fire. Notably, many Ravenclaws joined Dumbledore's Army and fought in the Battle of Hogwarts along with Gryffindors and Hufflepuffs.


(Taken directly from the harry Potter wiki, found here.)