IELTS is the key language test whose score is considered as evidence of your proficiency in the English language. This is if you are immigrating to Australia from India or from another nation. You must have good IELTS score as English is the primary language of Australia.
Alternatively, applicants have an option of taking up PTE (Academic) or TOEFL or OET or CAE English Tests as well as per the requirements of the respective authorities under skilled migration.