Product-market fit is the alignment between a product's value proposition and the opportunities of its target market, indicating that the product's value proposition satisfies a real need or demand in the market to a degree that customers are willing to pay for it.

Achieving initial product-market fit is a critical milestone for any product because it indicates that the product has found a solid foothold in the market and has the potential for long-term success and growth.

It's important to note that product-market fit is not a one-time achievement; it's an ongoing process that requires continuous monitoring, iteration, and adaptation as market conditions and customer needs evolve.