Hi Lydia. Our satellites tell us all sorts of things about the Earth! We build a lot of Earth imaging satellites so they take photos of the Earth for us to study. We can use them to track things like deforestation, illegal pirating, farming (seeing how well crops are growing), tracking shoals of fish in the see (by looking for the plankton they feed on), monitor areas hit by a disaster, like a hurricane or earthquake. We also build satellites which have instruments on to study things like the atmosphere, the weather or evening the gravity field of the Earth!