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 todays 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...