A key concept in finance is the investment portfolio, which refers to a collection of assets owned by an individual or institution. These assets can include real estate and physical assets like gold bars, but the majority of portfolios are made up of securities such as stocks, bonds, mutual funds, and exchange traded funds. When planning for retirement, it is important to diversify your portfolio with a mix of investments, ranging from safer options like US Treasury bonds to riskier investments like small-company stocks. This strategy aims to minimize market losses and maximize potential gains for a well-rounded retirement portfolio.