What is meant by "vested"?

All plans have vesting requirements. Such requirements dictate the period of time an employee must be employed before being guaranteed retirement benefits upon retirement. For example, under some plans the vesting requirement is 5 years. Therefore, an employee must work for 5 years before earning a guaranteed pension under the Plan. If the employee terminates employment after 6 years, such employee will still be eligible to receive a pension based upon the 6 years he/she was employed. However, if the employee terminates after 4 years, all benefits are forfeited.