Dear Anup, Joint Admission Test is an Entrance Examination for admission into Post graduation courses like M.Sc in IITs, IISc, IISER, NISER and NITs. And if you ask which is the top college, theses are all in the Top colleges list. Infact they are IITs and IIScs. They are the elite colleges. JAM 2019 was conducted by IIT Kharaghpur. The results have been announced on March 19th. However, if you want to appear for JAM 2020, please go through this website for 2019 details like eligibility criteria and procedure: http://jam.iitkgp.ac.in/?id=p&n=104