In simple terms, a pickup is the bit of a guitar that ‘listens’ for the strings being played (i.e. it ‘picks up’ string movement). The pickup is constructed of two key elements, a magnet and many turns of wound copper wire. This creates a magnetic field, in which the guitar strings lie. When the strings are moved, this disturbs the magnetic field, creating changes in the current passing through the coils of copper wire. This current then flows through the output of the guitar and on to the amp, where the process is reversed, in essence.