The Graduate Management Admission Test is a Standardized test that measures verbal, mathematical and analytical writing skills. It is intended to help the graduate schools of business assess the potential of applicants for advanced study in business and management. Nearly 900 management institutes all over the world (almost all of them in the US) require GMAT scores from each applicant.
The GMAT tests the fundamental skills - Reasoning and Comprehension included - and does not require any subject-specific theoretical study.
The test is designed in such a way that it would be unlike any other test you would have taken at school or college. First, the test has no question paper or answer sheets, nor does it have the same set of questions for all the examinees. Further, it does not give you the option of not answering a question (unless, of course, you run out of time at the end). All this because the GMAT is now an entirely Computer based test - the keyboard and mouse do the work of a pen or pencil. The test is scored out of 800 (in multiples of 10), and most scores fall in the range of 500-600. However, a score of even 800 is not unheard of!
The GMAT is only one of several parameters which the graduate schools look at to determine the selection of an applicant. A high score alone does not translate into an admission offer from a great school. But the test can be looked upon as the first major hurdle to be cleared in the process of getting admission into a B-school of your choice.