Interest Rate Risk

Can someone explain in simple terms why the coupon rate and YTM are inversely related to interest rate risk? (One goes up, the other goes down).

You should try to search for this one; there are a bazillion threads on this, as it gets asked multiple times every year.

While you’re doing that, think about the effect of coupon rate and YTM on Macaulay duration; as Macaulay duration goes, so goes modified duration (and, therefore, interest rate risk).