GMAT
The Graduate Management Admission Test (GMAT) 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 for admission to the MBA program.
The GMAT tests the fundamental skills - Reasoning and Comprehension included - and does not require any subject-specific theoretical study.
http://www.infozee.com/tests/gmat/about-gmat.htm
TOEFL
The Test of English as a Foreign Language (TOEFL) is required for international students seeking an admission in US universities and colleges for higher studies. TOEFL measures the ability of non-native speakers of English to use and understand North American English as it is spoken, written and heard in college and university settings.
Most people who take the TOEFL test are planning to study at colleges and universities where instruction is in English. In addition, many government agencies, scholarship programs, and licensing/certification agencies use TOEFL scores to evaluate English proficiency.
Currently more than 4,400 two- and four-year colleges and universities, professional schools, and sponsoring institutions accept TOEFL scores.
The TOEFL test measures English language proficiency in reading, listening and writing and is offered on computer in most regions of the world. In areas where access to computer-based testing is limited, a paper-and-pencil version of the test is administered.
IELTS
IELTS is an English Language Proficiency test that is required to be taken by non-native students for study in countries where the medium of instruction is English. Among the popular study destinations IELTS is accepted by universities in UK, Australia, New Zealand and Canada. It has become a mandatory test for study in Australia.
You cannot be granted an Australian student visa without an IELTS score, TOEFL is not accepted.
All other study destinations either require you to take the TOEFL or IELTS. IELTS is however not accepted by most universities in USA.
