Rupert Giles is Sunnydale High's librarian -- and the Watcher in charge of the Slayer. He comes from a long line of Watchers--his father and his father's mother were Watchers. But Giles wasn't always such a stuffy, book type. Not only was he in a band during his youth in England, but he and some of his friends would experiment with voodoo and crafts, and raising a few demons. He once revealed that he would have liked to have been a grocer or a pilot, anything as long as it wasn't a Watcher. Giles worked at the British Museum before coming to Sunnydale.
Giles is not just Buffy's Watcher, he's also a friend. he's very concerned about her welfare, and her life as a social whole. Despite protests, he often gives in when she wants a night off to just be normal.
Due to his tendency to spend enormous amounts of time with books and teenagers Giles has a nearly nonexistent social life. Eventually Giles developed quite a crush on the new Computer Science instructor, Ms. Calendar, and found himself embarrassingly tongue tied whenever he tried to ask her out. When Ms. Calendar was killed by Angelus, Giles took her death very hard, and misses her terribly.
Giles is full of strange bits of knowledge -- trivia, tidbits, mundane facts -- on subjects ranging from ancient history to the occult, to the strange and bizarre. He is educated and can speak five languages. Giles is also the current keeper of the Watcher Diaries, which are the recorded events of all past Watchers, their Slayers, and the Vampires they encounter.