The document discusses the term structure of interest rates, which refers to the relationship between interest rates and the time to maturity of debt securities. It specifically focuses on how the yield curve is constructed based on Treasury securities of different maturities. To construct the term structure, spot rates are determined for theoretical zero-coupon Treasury securities of different maturities by considering the theoretical value of coupon Treasury securities as a package of zero-coupon securities. The graphical depiction of the relationship between spot rates and maturities is called the spot rate or theoretical spot rate curve.