YTM is a crucial concept in fixed-income investments, representing the total return anticipated on a bond if it is held until it matures. It includes all cash flows from the bond (the annual coupon payments) and the difference between the purchase price and the face value of the bond at maturity. YTM assumes that all coupon payments are reinvested at the same rate and provides investors with a single figure that summarizes the bond's expected performance. It is calculated using the present value of expected future cash flows, which includes periodic coupon payments and the repayment of the bond's face value at maturity, discounted back to the present value using the YTM itself as the discount rate.