Fidelity Series Bond Index Fund is an open-end mutual fund that seeks to track the performance of the Bloomberg U.S. Aggregate Bond Index, which is a comprehensive benchmark for investment-grade, U.S. dollar-denominated, fixed-rate taxable bonds. Its primary function is to provide investors with broad exposure to the U.S. investment-grade bond market, including government, corporate, and securitized debt. The fund takes a passively managed approach, investing at least 80% of its assets in securities held by the index and is categorized as an intermediate core bond fund, balancing interest rate sensitivity and credit quality. Notable features include its low expense ratio, no minimum investment requirement, and monthly income distribution. With thousands of individual bond holdings, the fund offers diversification across sectors, primarily weighted toward U.S. Treasury and government-backed securities, but also including corporate and mortgage-backed bonds. As part of Fidelity’s institutional series, this fund is designed to deliver efficient, low-cost core bond market exposure, making it significant for institutions and individuals seeking stable income and modest capital appreciation within the fixed income segment of the financial market.