You had a broad sweep of History at Key Stage 3, but GCSE is the real starting point for future History study. The main difference between GCSE and IGCSE (or A Level and IAL) is that you are not required to study any British History at IGCSE, though you can if you want. This is advantageous for students studying outside the UK.
The aim at the heart of GCSE is the development and extension of students’ knowledge and understanding of local, British, and wider world history, but it goes further in order to gently prepare you for study at a higher level: You engage in historical enquiry to develop as independent learners and as critical and reflective thinkers. This is essential for study at either A Level, IB or undergraduate level History. You develop the ability to ask relevant questions about the past, to investigate issues critically and to make valid historical claims by using a range of sources in their historical context. You acquire an awareness of why people, events and developments have been considered historically significant and how and why different interpretations have been constructed about them. Lastly, you learn to organise and communicate historical knowledge and understanding in different ways and reach substantiated conclusions.
The balance of knowledge and skills learnt at GCSE should prepare you for study at A Level or IB.