Retirement systems are structured plans designed to provide individuals with income after they stop working. These systems can be public, like Social Security in the United States, or private, such as 401(k) plans offered by employers. They help ensure financial stability during retirement by allowing individuals to save and invest money over their working years. There are different types of retirement systems, including defined benefit plans, which guarantee a specific payout, and defined contribution plans, where the payout depends on investment performance. Understanding these systems is crucial for effective retirement planning and achieving long-term financial security.