Dividend yield is a company's annual dividend per share divided by its current share price, expressed as a percentage. A $100 stock paying $3 a year in dividends has a 3% yield.
Because yield includes the share price in its denominator, it moves even when the dividend itself doesn't: a falling share price mechanically raises the yield, and a rising one lowers it. A yield that looks unusually high relative to a company's peers is worth checking carefully — it can mean the market is pricing in a dividend cut, not that the stock is simply generous.
Not every company pays a dividend. Many growth-focused companies reinvest all profit back into the business instead, and have no yield at all — that is a deliberate capital-allocation choice, not an oversight.