Lily Potter, née Lily Evans, is the wife of James Potter and the mother of Harry Potter. At Hogwarts, she was in Gryffindor. She and James die at the hands of Voldemort when Harry is about a year old. She is remembered for her red hair, bright green eyes, and her strong love for her son — enough to die to protect him.
In Canon Edit
Lily Potter's character is somewhat ambiguous for most of the book series, as she's dead by the time the story begins. Her character is fleshed out in backstory, and through the words of people who fondly remember her.
She is Muggleborn, and the sister of Petunia Dursley (née Evans).
Lily Potter comes across as a kind, intelligent woman, and not afraid to speak up against injustice. She was part of the first Order of the Phoenix.
She was a member of Horace Slughorn's Slug Club (a club of talented and connected students that he reaped the benefits from) and she was a top student and Head Girl in her seventh year at Hogwarts. She was a talented witch with a knack for potions and charms.
Her Patronus was a doe.
Lily Potter is remembered fondly by most everybody she is mentioned by, except for Petunia Dursley, who was jealous of her witch sister.
Lily Potter was a brave woman — brave enough to defy Voldemort on several occasions.
Snape held romantic feelings for her even past her death. When they were in school, she protected him from the teasing of the four Marauders, but the friendship broke off afterward when Snape insulted her in his humiliation... and did not deny he planned to join the Death Eaters.
At this time, she considered James Potter 'an arrogant toerag', but later she fell in love with him, and they married.
In Badfic Edit
Lily Potter has a vague character, so it is easy for fangirls to turn her into a Mary Sue... but that's decently rare — more often she stands in the way of a bad slash story between James Potter and Sirius Black, or is paired with Snape, or even becomes a pointless naysayer.
She is rarely bashed, but more often rendered ineffectual.