Born: c. 1980.
Hogwarts first year: 1991 (PS7).
The best friend of Parvati Patil, Lavender tends to squeal and giggle a lot, and generally gives the impression of being silly; she's keen on Divination, for instance, having been convinced of Trelawney's powers after a vague prediction on the first day of class turned out (from one point of view) to have predicted the death of her pet rabbit, Binky (PA8). (Note that she didn't bring Binky to Hogwarts with her, although the rule about cats, owls, and toads only isn't mentioned.)
Lavender attended the Yule Ball with Seamus Finnigan (GF22, OP11). Lavender was Ron’s girlfriend for few months in their sixth year; their relationship consisted mostly of making out. Ron wanted desperately to end it after awhile, but didn’t know how (HBP21, DH7).
Lavender's saving grace is that she had the courage to be chosen for Gryffindor; during Hagrid's disastrous experiment to determine whether Blast-Ended Skrewts hibernated (they do not), Lavender, far from fleeing with the Slytherins, stayed to help and got burned (GF22). Unlike Seamus, Lavender joined Dumbledore's Army when it first formed (OP16), and she fought in the Battle of Hogwarts (DH31).
Name associations by MLW
"lavender" = from Latin "lavare" to wash (because the plant lavender is used to perfume things by being washed with them).
In flower symbolism lavender symbolizes affection; cleansing; or concealment (something packed away can be said to be 'in lavender'). Lavender's herbal properties include the promotion of sleep and sound rest, another reason why sheets and linens were scented with it.
It is also the color associated with clothing made for elderly ladies.
Pureblood? Not in canon
In 2001 Rowling flashed a notebook during a BBC interview that showed her notes on the students in Harry Potter's year and Lavender is noted as being a Pureblood in Gryffindor House. Lavender's ancestry cannot be considered canon until Jo reconfirms it, however, because the notes conflict in too many places with the stories as they were actually published.
In the movies
In the movie "Harry Potter and the Prisoner of Azkaban," the role of Lavender Brown was played by Jennifer Smith. In "Harry Potter and the Half-Blood Prince" and both parts of the "Deathly Hallows" films, she was played by Jessie Cave. In the final battle scenes in the film, Lavender is seen lying on the ground being attacked by a werewolf. Some fans have mistakenly assumed that the character dies in the film, but this isn't true. This is a literal depiction of the scene in the book:
"'NO!' shrieked Hermione, and with a deafening blast from her wand, Fenrir Greyback was thrown backward from the feebly struggling body of Lavender Brown." (DH32)