Observational data has lead us to believe that the Universe is undergoing an accelerated expansion. This acceleration canonly be driven by a component which has a negative pres-sure, the cosmological constant or other exotic models suchas the ‘dark energy’. Understanding the nature of dark en-ergy is the focus of many current studies, and its origin being unknown, these studies are largely focused on model building and constraining its parameters. In this article, we discuss how the accelerated expansion of the Universe is driven by dark energy and how dark energy parameters are constrained by observations.