This workshop, shortly after GLAST's launch, is one of the first occasions to understand the new opportunities opened by the satellites in orbit, and it is devoted to the sources that will profit more from broad-band (GeV-TeV) observations, possibly giving answers to many astrophysical issues. Among these there are galactic sources, like pulsars, where a precise measurement of the energy cutoff of the pulsed spectra can discriminate among many competitive acceleration scenarioes. There are also extragalactic sources like active nuclei, where broad-band measurements effectively probe the inner structure of the gravitational engine, or Gamma Ray Bursts (GRBs) where observations by the LAT instrument (on-board the GLAST observatory) may trigger important follow-up with Cherenkov telescopes. Moreover, the observation of sources located at medium redshift (0.2 < z < 0.5 for Cherenkov and z ~ 1 with GLAST) heavily constrains the EBL, either requiring to refine the evaluation of EBL's components or even to invoke new physics. The workshop will also introduce the participants to the intricacies of the analysis at very high energies, where data have usually to be mined in a much larger background. Given the presence of many veterans in the field, a special session will be devoted to data analysis and to an overview of the available analysis tools and techniques.