1. Academic- Candidates who wish to go abroad to study have to take IELTS Academic test.
2. General- Candidates who wish to go abroad to work or retire have to take IELTS
Originally, IELTS was launched as a paper based test. But now, in many countries, Computer Delivered IELTS is also available for both Academic and General test takers.
Most of the educational institutions and organizations in Australia, Canada, USA and Britain accept the IELTS score.
An individual can attempt for the test multiple times if he/she is not satisfied with the score. Also, there is no rule that the next attempt has to be made after a given period of time. They can re-take it whenever they wish to. Furthermore, during the application, the best score out of all the tests can be submitted, that is, the average score is not calculated.