The Early Universe
Though much of the universe is filled with empty space, portions of it, especially in galaxies, contain clouds of gas and dust that obstruct our view of far away objects. These clumps of gas, as well as galaxies and stars, are the result of wrinkles in the shape of the early universe that expanded during the big bang. Nowadays, these expanded wrinkles are responsible for the formation of the galaxies and gas clouds that fill our view of the universe. Fortunately, Gamma-Ray Bursts are so bright that some of the light from these explosive events still reaches Earth after passing through all the gas and dust.
The Gamma-Ray and X-Ray light that reaches us isn't blocked by the gas and dust, so measuring this tells us how bright the burst was. The optical light the GRB gives off can be blocked and absorbed by the gas and dust, so by observing this and comparing it to the gamma-ray light brightness, scientists can figure out how much light was blocked and what kind of stuff blocked it.
By working together, both parts of the telescope provide information about the intergalactic medium like the concentration and the composition of the gas and dust. This gives scientists an idea of how these clouds formed, giving hints about the formation of the wrinkles in the early universe.