The study of the universe, nowadays referred to as cosmology is considered one of the oldest sciences existing. Already Hipparchus wondered about our universe and its fate. The advancement in our understanding and technology since then has allowed us to challenge old concepts and accept new ones. One of these concepts is Dark Energy, the study of whose properties keeps physicists busy all over today''s world. This book shows how observations, in particular SNe, relate to different theoretical models of our universe. We recall the basics of cosmology and derive some important theoretical results. Subsequently the concept of Dark Energy is introduced as well as the dynamics and observations involved. In the end we analyze a few different models of Dark Energy employing the tools developed throughout the book. Will many models be rejected in the future? Can we say for sure "oh this is the right model" or these are the most promising? Written like a story, this book tells the tale of our universe as it is and what it is. It is simple yet detailed enough to appeal to a wider audience.