In many ways, a pension plan is a method in which an employee transfers part of his or her current income stream toward retirement income. There are two main types of pension plans: defined-benefit plans and defined-contribution plans.
In a defined-benefit plan, the employer guarantees that the employee will receive a definite amount of benefit upon retirement, regardless of the performance of the underlying investment pool.
In a defined-contribution plan the employer makes predefined contributions for the employee, but the final amount of benefit received by the employee depends on the investment's performance.