The Nuveen Municipal High Income Opportunity Fund (NMZ) is a mutual fund that primarily invests in municipal bonds, which are issued by state and local governments to fund public projects. This fund aims to provide investors with a high level of tax-free income by investing in a diversified portfolio of municipal bonds with varying maturities and credit ratings. It may also invest in other fixed-income securities, such as corporate bonds and preferred stocks, to enhance its income potential. With a focus on high-yield municipal bonds, NMZ offers investors the opportunity to earn attractive tax-exempt income while also potentially benefiting from the stability and tax advantages of municipal bonds.