The process of star formation constitutes one of the main problems of modern astrophysics. As compared to stellar evolution it is very ill understood problem. Young stellar object (YSO) denotes a star in its early stage of evolution. Census of young stellar objects (YSO), correlation of their physical properties with ionizing source/s and their spatial distribution in a molecular cloud, are some of the signatures used to study the time-scale and star formation processes in a given region. In this talk I will talk about the various kind of star formation mechanisms, particularly focusing on the star formation on the edge of HII regions, a brief introduction about the YSOs. I will conclude my talk with, how studying YSOs helps us to understand star formation process.