Active Galactic Nuclei (AGN) are among the most luminous and mysterious celestial sources, thought to be powered by the accretion of matter onto a supermassive black hole. In this thesis, I investigated the hard X-ray radiation of AGN, with a main focus on the X-ray reflected emission, in order to obtain a better insight into the geometry and physics of these sources. This was achieved by studying the NuSTAR observations of a large sample of nearby AGN. Local AGN were found to feature a large range of spectral shapes above 10 keV. In unabsorbed AGN, the hard X-ray spectrum is shaped by the dynamics of the X-ray corona, while the spectrum above 10 keV of absorbed sources is shaped by the torus' characteristics. Moreover, the continuum X-ray emission was found to differ between absorbed and unabsorbed objects, which might hint the existence of intrinsic differences between the two groups.