Some of the most important open questions in astrophysics concern how and when active galactic nuclei (AGN) are triggered, and how important they are in the evolution of galaxies.In order to understand these processes and interpret the results found for AGN at cosmological distances, it is fundamental to account for the structure of their central engines in the local universe. This includes the unifying torus, whose properties are still uncertain. Thus, the first objective of this proposal is to characterize the AGN obscuring torus using an infrared survey of a homogeneous sample of nearby active galaxies. We will use mid- and far-infrared data obtained with the CanariCam instrument on the 10 m Gran Telescopio Canarias (GTC) and the Herschel Space Observatory, respectively. This survey will represent the definitive characterization of the AGN torus in the local universe. In addition, we will use new spectropolarimetric observations of a smaller sample of Seyfert galaxies to test the validity of the clumpy torus squeme, and ultimately, of the unified model for AGN.The second objective of this proposal is to confirm the hypothesis that AGN of different luminosities are triggered in different ways, with galaxy interactions triggering luminous AGN (quasar-like), and secular processes (bars or disc instabilities) triggering lower luminosity AGN (Seyfert-like). We also aim to investigate the role of other factors such as the environment in the triggering of the nuclear and star formation activity, and the connection between them.The results of the proposed project will substantially enhance our understanding of the physics of AGN and their role in galaxy evolution.