Hello Naushad, Both CAT and MAT are national level examination examinations for admission in B school across the country.Both the examinations are fairly popular in the country and are widely accepted. Some institutes accept both CAT and MAT scores.
CAT is a mandatory entrance exam conducted by the IIM’s. This is the first stage in the admission process to all the six IIMs. Other than IIMs other business schools also consider the CAT scores as the main eligibility criteria for enrolling students in their management courses. AIMATS conducts the MAT exam and it is known as the National Entrance Test for MBA and similar programs like PGDM. MAT is carried out four times in a year were as CAT is only once every year. The A-graded business schools review CAT scores where as MAT is reviewed by B-grade schools in the country.The difficulty level of CAT is more than MAT.
Best of luck.