As the name implies, a yield curve is a curve (chart) that shows the yields asked by the investors to buy US Treasury Bonds. It has bond maturities on the x-axis and the yields (interest rates) on the y-axis. The short-term end of the curve refers to the yields the US treasury has to pay on one-month to two-year maturity debt. The long-term end refers to the yields for longer maturities, such as 10-year to 30-year bonds. US treasury yields are also called "risk-free" rates, as no one expects the US govt to default.