Study of absorption line systems seen in the spectra of distant QSOs, has played a remarkable role in probing the evolution of the Universe. Tremendous amount of research has been done on absorption line systems e.g. Lyman-alpha forest, Lyman-limit and Damped Lyman alpha systems along the line of sight of QSOs which is a unique tool to prob the proto-galaxy at high redshift. Their studies are important in predicting the physical and kinematic properties of intervening galaxies and IGM. With this idea I will discuss the major research and conclusions made in the field of astronomy from the studies of QSOABL. At the end I will relate my research work with the study of the absorption system of these high redshift objects