What are seismograph and what do you do with them?

A seismograph is an instrument used for recording the intensity and duration of an earthquake.its a machine that records the earthquakes waves.

First

Earthquakes generate seismic waves which can be detected with a sensitive instrument called a seismograph. Advances in seismograph technology have increased our understanding of both earthquakes and...

there is no difference because it is the same thing.

A seismograph is a diagram that shows the activity of an earthquake. The longer the line on the diagram, the more violent the shaking of the ground is.