IELTS stands for International English Testing System
TOEFL stands for Test of English as a Foreign Language
IELTS is jointly owned by University of Cambridge, British council and AEO.
TOEFL is a registered trademark of Educational Testing Service
Both IELTS and TOEFL are recognized by more than 6,000 institutes all over the world, in fact 8,000 institutes in the world recognize TOEFL.
Over the years IELTS has been more popular than TOEFL because people consider it easier than TOEFL