Thanks, it is a tricky question and much debated. Depends on what lens you want to look at it. Is it mainly about how a chip operates on the inside or what it looks like on the outside?

I choose to explain it as a philosophy around how to make a chip given a budget of transistors: https://itnext.io/risc-vs-cisc-microprocessor-philosophy-in-2022-fa871861bc94