GATE is conducted jointly by the Indian Institute of Science (IISc), Bangalore and the seven old IITs on a rotational basis every year.
It is mainly held for admission of graduate engineers to postgraduate courses in engineering/technology (ME, MTech, and PhD) at premier educational institutions. Many other top universities and colleges accept GATE scores for admission. GATE scores are also used for PSU recruitment.
IIT JAM is held by any one of the seven old IITs for admitting candidates with BSc and applied sciences degrees to post-graduation courses offered by IITs, IISc, IISERs, NITs, and other top institutes.
Those who qualify IIT JAM can get accepted to master's degree courses in science such as MSc (four semesters), Joint MSc and PhD, and MSc-PhD dual degree among others.
About different exam papers and validity of scores
GATE is conducted for 25 engineering disciplines while IIT JAM has papers for seven subjects, including Mathematics, Physics, Chemistry, Mathematical Statistics, Geology, Biological Science, and Biotechnology.
GATE score of a candidate is valid for up to three years while IIT JAM score is valid only for one year. However, GATE scores are valid for three years only for postgraduate admissions and not PSU recruitment.