In the last two decades, cosmology has undergone a revolution, with a large influx of high quality data. There is now a consensus cosmological standard model, Lambda-CDM, based on General Relativity as the theory of gravity, and which requires only about 4% of the energy budget of the universe to be in known baryonic form. The rest is divided into two apparently distinct, dark components: Cold Dark Matter (CDM) and cosmological constant. The simplest explanation for CDM is a weakly interacting particle, still to be detected; he cosmological constant is the simplest term that can be added to the Einstein equations that can give rise to the observed accelerated expansion of the universe but has no compelling explanation within our current understanding of fundamental physics. Thus, more complicated terms, collectively called the Dark Energy, have been proposed. In this talk, I give a short overview of the physics behind these two dark components, emphasizing their impact on cosmological observations. I then discuss alternatives based on modifications of the Einstein equations also aimed to explain cosmological observations. I will discuss the need for a parametrized model-independent approach to cosmological observations and conclude with future expectations.