The Slayers Handbook
Giles
The Watcher
The Watchers job is to help, train and watch the Slayer. Every Slayer has a Watcher, and Giles is Buffy's Watcher.
The Watcher works for the Watcher's Council, who's job it is to find the new Slayer and moniter the actions of the Slayer and her Watcher.
Rupert Giles worked at the school Library until the end of season 3 when the school was blown up by them. Bored with being a man of leisure in season 4, he bought the shop called the "Magic Box", a shop which sells both real magical items as well as tourist items.
As a teenager the calm watcher was called "Ripper", hated the world, and abused magic by summoning a demon to possess them giving them a huge high.
In Season 6 Giles leaves Buffy to go to England. There was 2 reasons for this. The first is to porve to Buffy that she can cope with out a Watcher, that she canm't and won't give in no matter what. The second was to start off another Spin-off series in which Giles will become the main character. This will be stranger than "Angel", as then shows have the same idea's, where as Giles hasn't got the Physical strength to fight Vampires. Sources say that it will be more Ghosts and Spirit's that Giles will be fighting.