CAT is a National level Common Entrance test to pursue MBA in IIM's and Business Schools. To write CAT exam one  must have passed graduation from a recognised Board of University. Final year graduation students are also allowed to write the CAT exam. If you do MBA in an IIM or Top B school, the career and placement opportunities are excellent. As a fresher one can earn minimum 5-10 lakhs after MBA.

In addition to that CAT exam is of 3 hours duration comprising of Verbal Ability and Reading Comprehension, Data interpretation and Logical Reasoning, Quantitative Aptitude.

All the best.,