The term Product-Market Fit describes the fact that a product matches market needs.
When a product has Product-Market Fit it starts 'resonating' with buyers and market traction picks up. Marc Andreessen describes Product-Market Fit as:
"you can always feel product/market fit when it’s happening. The customers are buying the product just as fast as you can make it — or usage is growing just as fast as you can add more servers. Money from customers is piling up in your company checking account. You’re hiring sales and customer support staff as fast as you can."
Product-Market Fit is a desirable state for all products. The idea applies at various levels, starting with Problem-Solution Fit and ideally leading towards a good Business-Market Fit.
Indications of good Product-Market Fit are: