A key difference between bonds and equities is how they are affected by rising interest rates. As interest rates go up, bond prices go down. For a fixed income investor, they will see the price of their investment decline in a rising interest rate environment. If the bond holder keeps the investment until the maturity date, they will still receive all of their initial investment back, assuming the borrower is still credit-worthy. However, if the investor purchased the fixed income in an ETF or a mutual fund, then the value of the fund will decline as interest rates increase.
Equities are not directly affected by rising interest rates in the same way that bonds are. Some equities do better than others in a rising interest rate environment. For example, equity in a company which has high debt may be more subject to rising interest rates than a company with no, or very little, debt. So the value of the equity for the highly-leveraged company could decline as interest rates rise, or at least not rise as quickly as a company with very little debt. Equities are more prone to volatility than bonds, in large part because equity investors take into consideration countless factors.