A bond mutual fund focuses on investing in bonds with maturities that fall between 5 and 10 years. These bonds offer a moderate level of risk and potential for return. Investors can diversify their portfolio by including bond mutual funds, as they provide stability and steady income over time. It's important to carefully consider the credit quality and interest rate risk of the underlying bonds before investing in a bond mutual fund. Overall, bond mutual funds offer a balanced and strategic approach to building a diverse investment portfolio.