Pickups are magnetic microphones under the strings they got the vibe of the strings and that electric variation is drawn to the amp which amplifies that tiny variation, wikipedia will help you even better.
http://en.wikipedia.org/wiki/Pickup_%28 ... hnology%29
The pickups on the guitar you're about to get one of these centuries are damn fine, they have their own personality, so buy the babe and post a picture then we'll continue discussing abouts pickups, strings, amps and stuff