JAM stands for JOINT ADMISSION TEST for M.Sc.(masters in science) or other PG courses. 

therogh this exam you can go for admissions into IITs and IISc that is the Indian Institute of technology and Indian Institute of Science.

sorry but you are late this year as the applications start from september and the admit cards are issued by january.

better luck next time.

this course is for different streams like maths, physics, biological sciences, biotech, stats.

yes you have good scope in this field as you get to study from renowned institutes and hence further you can enter either the teaching program or phD AS PER YOUR CHOICE. if you wish to enter the research field you can even step abroad.

all the best and stay updated.

refer to link http://jam.iitb.ac.in/