IELTS stands for International English Language Testing System. The IELTS English test is an internationally-recognised system for testing English language. It is designed to measure ability to communicate in English across all the four language skills – listening, reading, writing and speaking – for people who intend to study or work where English is the language of communication.
If you aim to study at university level in the UK, you will be required to take an IELTS English test and get the required score. The universities in Canada, Australia, New Zealand, and Ireland also recognise the IELTS examination and it also recognised by the immigration authorities in the UK, under such as the new points based immigration system.