Seismograph is a long sheet of paper with measurements of seismic activity, (earthquakes, explosions, etcetera). It will look like a long sheet with sgwiggily lines on it. These lines are made by a pen on a weight going back and forth due to the seismic activity which causes every to move about.
The amplitude of the sgwiggle lines (height of sgwiggle) is proportional to the strength of the activity, naturally.
These can be very helpful around the world because from at least 3 seismographs situated around the world, earthquake origins can be found in order to warn near by civilians and possibly to make evacuations for coasts in cases of sea earthquakes forming tsunamis.