Just confused with the bond concept learnt from books. I concluded something in my own words and hope somebody can correct me if anything's wrong.

The actual price of a treasure bond is calculated as discounting each cash flow with different rate on the term structure, and this rate is called spot rate for zero coupon bond. the spot rate is no a given, it is set by the government, but we can derived it from the treasure bond on the market. For a corporate bond, the rate is the spot rate plus some risk premium. So, if the above is true, then YTM is a measurement of bond by using one single rate to discount all cash flow. And the spot rate changes everyday, therefore the price of bond tomorrow is calculated by using a new set of term structure.

One more question, if all above is true, so what does the U.S treasure yield curve on Yahoo bond center stand for? I compared the rate on the yield curve with the YTM of zero treasure bond with the same term structure, I found that they do not match.