Nuveen Select Tax-Free Income Portfolio 3 operates as a diversified closed-end investment vehicle. Its primary objective is to generate a consistent stream of income and stable dividends, which are exempt from federal income taxes and, where applicable, from designated state income taxes. This goal is pursued while prioritizing the preservation of capital, mainly by allocating assets to a portfolio of municipal obligations. The fund's holdings are broadly distributed across various sectors, including general and limited tax obligations, healthcare, transportation, consumer staples, and U.S. government-guaranteed securities, among others. Geographically, its investments encompass a wide range of states and territories, such as California, Illinois, Texas, New Jersey, Colorado, Washington, Florida, Virginia, New York, Missouri, Iowa, Michigan, Minnesota, and Nevada. The management of this portfolio is overseen by Nuveen Fund Advisors, LLC, which is a division of Nuveen Investments, Inc. (commonly referred to as Nuveen).