Two important scientific questions about blazars are partially but not completely answered at this point. First, how is the gamma-ray spectrum produced? In many cases the gamma-rays dominate the bolometric luminosity, at least during flare states, so gamma-rays are fundamental to understanding how the bulk of the energy is produced in blazar jets.
Second, there are several sub-classes of blazars with distinct spectral characteristics but the physical origin of this difference is not understood. Some blazars have very strong emission lines and so are classified as quasars while those with very weak emission lines are classified as BL Lac objects, and among the BL Lac objects, there are two flavors (see next) with different continuum shapes. The differences among these types of blazars are likely a clue to their underlying structures.