Abstract: Neutron stars are extremely compact objects with an average density higher than that of the saturate nuclear matter. Exploring the nature of such objects can help us to understand physics under extreme conditions, especially the gravitational and strong forces. This paper introduces the concepts of pulsars and neutron stars, as well as various models of the interior structure of the latter. More importantly, we shall show how to test such models observationally by determining various properties related to the equation of state, such us the maximum mass and tidal deformability. Detecting further merger events of binary neutron stars and/or neutron star-black hole binaries will certainly help to unveil the inner structure of neutron stars.