I believe it refers to both, 2 for 1! For the purpose of the exam I just remember the formula if they ask to calculate and the theory if they ask about strategy. Hope this helps…
Per Investopedia:
Duration measures how long it takes, in years, for an investor to be repaid the bond’s price by the bond’s total cash flows. At the same time, duration is a measure of sensitivity of a bond’s or fixed income portfolio’s price to changes in interest rates. In general, the higher the duration, the more a bond’s price will drop as interest rates rise (and the greater the interest rate risk). As a general rule, for every 1% change in interest rates (increase or decrease), a bond’s price will change approximately 1% in the opposite direction, for every year of duration.
The duration of a bond in practice can refer to two different things. The
Macaulay duration is the weighted average time until all the bond’s
cash flows are paid. By accounting for the
present value of future bond payments, the Macaulay duration helps an investor evaluate and compare bonds independent of their term or time to maturity.
The second type of duration is called “
modified duration” and, unlike Macaulay duration, is not measured in years. Modified duration measures the expected change in a bond’s price to a 1% change in interest rates. In order to understand modified duration, keep in mind that bond prices are said to have an inverse relationship with interest rates. Therefore, rising interest rates indicate that bond prices are likely to fall, while declining interest rates indicate that bond prices are likely to rise.