GRE exam aims to measure verbal reasoning, quantitative reasoning, analytical writing and critical thinking skills that have been acquired over a long period of time and that are not related to any specific field of study. It is commonly known for admissions requirement for graduate schools in US and other English speaking countries for graduation program.
Once you clear GRE Exam you are eligible for admission, but weight of GRE scores vary considerably not only from school to school, but from department to department, and from program to program also.
The GMAT (Graduate Management Admission Test) is a computer-adaptive standardized test in mathematics and the English language for measuring aptitude to succeed academically in graduate business studies. Business schools commonly use the test as one of many selection criteria for admission into an MBA program. However, there are many business schools that also accept GRE scores.
The following are criteria of certain business schools:

• Harvard Business School: Official test scores for the GMAT or GRE tests no more than 5 years old.
• UVA-Darden: Will also accept a GRE score in place of the GMAT.
• MIT-Sloan:The GMAT or GRE is required of all applicants and must be taken before submitting your application.
• Penn-Wharton: Official test scores for the GMAT or GRE tests.
• Stanford GSB: The GMAT is required for admission. Will accept the GRE - including the GRE revised General Test — as an alternative.
• NYU-Stern: The GMAT is strongly preferred, but scores from the Graduate Record Examinations (GRE) will also be accepted.
• Chicago-Booth: Accepts either GRE or GMAT scores.
•  Vanderbilt-Owen : Accepts either GRE or GMAT scores.
• Berkeley-Haas: Without exception, all applicants to the Haas Ph.D. Program must submit official scores of either the GMAT or the GRE.
• Columbia Business School: Accepts GRE test scores in place of the GMAT, only if applicant has not taken the GMAT within the last 5 years.
• Johns Hopkins-Carey: Accepts either GRE or GMAT scores.
• Dartmouth-Tuck: Accepts either GRE or GMAT scores.
• Northwestern-Kellogg: Accepts either GRE or GMAT scores.

In comparison with GMAT's emphasis on logic, GRE measures the test-takers' ability more in vocabulary. This difference is reflected in the structure of each test. Despite the Analytical Writing section in common, GRE has analogies, antonyms, sentence completions, and reading comprehension passages in Verbal section, while GMAT has sentence correction, critical reasoning and reading comprehension.