Severus Snape

Severus Snape is a canon character in the Harry Potter books. He is a half-blood wizard and the only son of of witch Eileen Snape and muggle Tobias Snape. Severus Snape attended Hogwarts School of Witchcraft and Wizardry from 1971-1978 and was sorted into Slytherin while his best friend, Lily Evans, was sorted into Gryffindor.

Physical Description
Severus Snape was described to have shoulder-length, greasy black hair, a long nose, and crooked teeth. He was round-shouldered yet had very long, thin arms and legs. He had pale skin and big, black eyes.

Relationships
Lily Evans 

Severus and Lily grew up together and became best friends at a very young age. Severus was smitten with her the moment he met her and continued to be so for the rest of his life. While in school, Severus had befriended the group of pure-blood supremacists in Slytherin, therefore putting a strain on Lily and his friendship until it was terminated in their fifth year. After that, Snape tried desperately to win back Lily's friendship but could not succeed. He joined the Death Eaters, hoping that might impress Lily, but only made matters worse.

The Marauders

During his time at Hogwarts, Snape was repeatedly bullied by The Marauders, more specifically James Potter and Sirius Black. Because of this, Snape wasn't able to let go of the hatred he felt for James Potter, even when James had saved him from Remus on a full moon. Severus especially hated James when he lost Lily to him, to which Snape could never let go. During his seventh year, Snape didn't lose any opportunity to try and curse James, which led James to defend himself and fight back.