A primer on problems and prospects of dark energy

This review on dark energy is intended for a wider audience, beginners as well as experts. It contains important notes on various aspects of dark energy and its alternatives. The section on Newtonian cosmology followed by heuristic arguments to capture the pressure effects allows us to discuss the basic features of physics of cosmic acceleration without actually resorting to the framework of the general theory of relativity. The brief discussion on observational aspects of dark energy is followed by a detailed exposition of underlying features of scalar field dynamics relevant to cosmology. The review includes pedagogical presentation of generic features of models of dark energy and its possible alternatives.