Here are two quotes from the father of TRIZ. I think they get to the heart of what TRIZ is.
“I became more and more interested in the mechanics of creativity. How were
inventions made? What happens in the head of the inventor?” – Genrich Altshuller
“Although people who had achieved a great deal in science and technology talked of the inscrutability of creativity, I was not convinced and disbelieved them immediately and without argument. Why should everything but creativity be open to scrutiny? What kind of process can this be which unlike all others is not subject to control?…What can be more alluring than the discovery of the nature of talented thought and converting this thinking from occasional and fleeting flashes into a powerful and controllable fire of knowledge.” – Genrich Altshuller