"Greater Iran" is like a big family where everyone speaks similar languages and has similar cultures, but they live in different countries now. Long ago, a lot of people lived in one big place called Persia, which is now Iran. But some people moved away to other countries like Afghanistan, Tajikistan, and parts of Iraq and Pakistan. Even though they live in different places now, they still share a lot of things like language, religion, and traditions. That's why we call this whole area "Greater Iran."