What Does The Pickup Do?

[Syaffiq]

Hi, Kinda New To Guitar. What I Don't Understand Now Is What Does The Pickups Do And Why Are There 3 Way Switch For The Pickups. I Hope Someone Could Help Me As I'm Completely Clueless About This. Thanks!

 

[Godspeed64]

http://en.wikipedia.org/wiki/Pickup_(music_technology)

 

[skyflux]

Ahh .. I remember my physics text book explained that part..
Basically it converts those vibrations of the strings into electrical signals , then send it to a amplifier to amplify the signal (since the original is too weak) then viola , you got your sound.
Correct me if I'm wrong..