Severus Snape was born to Tobias Snape and Eileen Prince. Growing up near Lily Potter, Snape and her were best friends but Severus found it hard to live with his parents, as his father hated magic.
Severus started at Hogwarts with Lily in 1971, where he was Sorted into Slytherin House. This put him in the same year as Lily but unfortunately for him in rival houses. Severus became the immediate enemy of James Potter and Sirius Black and was a frequent victim of their bullying. This led him to be irritable towards James's son Harry when he was a professor. Snape, when young, developed a passion for the Dark Arts, which increased as his desire for revenge grew stronger. Snape became involved with the bullies in Slytherin House, many of whom were pure-blood supremacists. This put his friendship with Lily, a Muggle-born, under great strain until it was eventually broken in their fifth year. In an attempt to win back Lily's affections, Snape joined the Death Eaters along with a group of his fellow Slytherins.
Severus was made a member of the Slug Club presumably because of his talent at potion-making and Horace Slughorn kept a picture of him as a student, clutching his copy of Advanced Potion-Making. Despite this, Horace did not have many hopes for Severus's future, as his photograph was kept behind many others.
Shortly before Lily Evans was murdered by Lord Voldemort, Snape changed sides and became a member of the Order of the Phoenix as well as a double agent during the Second Wizarding War. With tremendous difficulty, Snape prevented Lord Voldemort from learning the truth about his loyalties. Despite the opinions of most others including Harry during his early life, Albus Dumbledore trusted Snape for reasons that were kept between them both until their deaths. Despite Snape killing Dumbledore, it is learned that they had a special agreement for him to do so. When he died, it was revealed that his deep strong love for Lily Evans caused him to redeem himself, joining Dumbledore's cause for her protection (and, after her death, that of her son) from Lord Voldemort.
