CIE stands for Cambridge International Examinations. Well its an examining board just like AQA, Edexcel. The exams are conducted by Cambridge Assessment which also makes OCR papers for UK students. international students like me do cambridge papers and I can tell you they are a little tougher than UK papers (AQA, OCR). And they are not modular. they are sat in june and november. the syllabus is not that much different from the other boards but the way the questions are asked can be.