How does a guiter works?

Shortly Explained-                

The energy of the vibrating strings is transferred to the soundboard through the bridge. The guitar's hollow body amplifies the sound of the vibrating strings. The pitch of the vibrating strings depends partly on the mass, tension, and length of the strings. On steel-string guitars, the lower strings are thicker.        

Electric Guitar- 

The electric guitar may be the most important and popular instrument of the last half-century in American music. Certainly its introduction brought a major change to American musical technology and has shaped the sound and direction of modern musical styles.

Pickup-    

Electric guitar pioneers tried a variety of ways to pick up the instrument's sound and amplify it. George Beauchamp and Paul Barth developed the first successful electromagnetic pickup system; it was applied to the Rickenbacker Frying Pan guitar, marketed in 1932. 

Today, pickups are electromagnets mounted under the guitar strings. They sense the strings' vibrations and convert them into electrical signals that travel through a cable to the amplifier to increase the sound. There are two kinds of pickups: single-coil and double-coil, or humbucking. The latter give a fuller sound.