"Defined benefit" plans promise you a monthly pension of a certain amount, usually based on your average income during your final years of employment, your age at retirement and your years of service, but there is no actual "account" set up for you. Other pans, called "defined contribution" plans, require the employer to contribute certain amounts each year to a retirement "account" established for you. A 401(k) plan is one type of defined contribution plan. Other types of defined contribution plans include profit-sharing plans, money purchase plans and employee stock ownership plans. And there are a lot of variations within these two broad categories of pension plans. It's important to know these terms because these two types of plans function differently and the law law treats them differently.