Abstract. This paper presents the results of a Ph.D thesis emphasizing the studies of various characteristics of Young Stellar Objects (YSOs) and their environment. The main objective of the thesis is to study the effects of mechanical and radiative feedback of massive stars on their surroundings including triggered star formation in Cometary Globules (CGs) and Bright-Rimmed Clouds (BRCs) situated at the borders of Galactic HII regions and time dependent interaction of Pre-Main Sequence (PMS) stars with their circumstellar environment through accretion and outflow processes. Some of the important results of this thesis are (i) star formation in BRC SFO~38 is triggered by massive OB type stars in HII region IC~1396 (ii) distribution of CGs at the border of HII region Gum~Nebula is shaped by photoevaporation powered by UV radiation of massive stars in Vela~OB2 association (iii) interaction of Herbig Ae star V351~Ori with its circumstellar environment is time-dependent and episodic in nature. Dynamic magnetospheric accretion and disk wind emerge as the most satisfactory model for interpreting the observed line profile variations of V351~Ori. The full version of the thesis is available from the Indian Institute of Astrophysics Repository webpage: http://prints.iiap.res.in/handle/2248/5529

Key words: stars: formation, pre-main-sequence -- ISM: HII regions, clouds