It is the relation between the interest rate (or cost of borrowing) and the time to maturity of the debt for a given borrower in a given currency. There are three main types of curves normal, inverted, and flat.
The rate of return anticipated on a bond if it is held until the maturity date. Yield to Maturity is considered a long-term bond yield expressed as an annual rate. The calculation of Yield to Maturity takes into account the current market price, par value, coupon interest rate and time to maturity.