  VERITAS is an array of four 12-m diameter imaging atmospheric-Cherenkov
telescopes located in southern Arizona. Its aim is to study the very high
energy (VHE: E > 100 GeV) gamma-ray emission from astrophysical objects. The
study of Active Galactic Nuclei (AGN) is intensively pursued through the
VERITAS blazar key science project, but also through the large MWL
observational campaigns on radio galaxies. The successful VERITAS AGN research
program has provided insights to the jet inner structures and started a more
detailed classification of blazars. Moreover, the synergy between Fermi and
VERITAS on blazar observations resulted in important constraints on the
extragalactic background light (EBL) through gamma-ray observations, and on the
cataloguing of the several AGN sub-classes . VERITAS discovered also the first
extragalactic non-AGN gamma-ray source. The discovery of gamma-ray emission
from the starburst galaxy M 82 by VERITAS and Fermi provides important clues on
possible mechanisms for accelerating cosmic rays.
