It is possible to recreate the early universe conditions (a few micro-second after the Big-Bang) at the relativistic heavy ion collider in BNL and Large Hadron Collider in CERN by ultra relativistic collisions of heavy ions such as Au-Au (Gold-Gold) and Pb-Pb (Lead-Lead) respectively. The form of the matter created at such extreme conditions is known as quark-gluon plasma (QGP) which is shown to be closer to a near perfect fluid. Investigations on the properties of the QGP throw light on the nature of one of the most complicated force in the nature viz. the strong interaction. In this book, an attempt has been made to understand bulk and transport properties of the QGP, by developing an effective quasi-particle descrition based on hot QCD (the underlying theory of strong interaction). The descrition thus obtained is married with the semi-classical transport theory to understand the transport properties of the QGP.