The search for product-market fit (PMF) is the state when your product perfectly meets the market's needs. I would call it the "gold mine" on the market. From my experience, I can say that this is one of the most challenging and fascinating stages of any startup's development.
Here, both a clear marketing approach and a bit of luck are important. Over time, intuition comes into play, which is not always infallible but sometimes helps guess what people really need.