Yield is the amount of yearly income that an investor would get from an investment.
If I buy a $100,000 25 year bond that has a 10% interest rate, I would receive money from that bond every year. $100,000 x .10 =$ 10,000. Every year for 25 years I would receive a check for $10,000. This is my yearly interest. This interest is also called my yield. This yield is most often expressed as a percent. People would say I have a bond with a 10% yield.