These are discussed in more detail in the following chapters. Defined benefit plans provide a payment at retirement, based on a certain percentage of income. These plans tend to favor long serving older workers because they usually earn the most pay toward the end of their careers. Generally, the payment level is based on a formula that computes your last few years of service, but you'll need to check the SPD for details. Defined benefit plans can be more expensive for the employer and because of this, more and more organizations are switching to a defined contribution plan or scaling back on benefits.
Some companies offer hybrid plans that combine some of the elements of both types of plans.
In a cash balance plan, for example, you get a certain percentage of your pay plus interest on the entire sum. If you leave the company you can often roll it over into an individual retirement account. But long term workers may not receive as much as they would in a traditional plan. Vesting refers to how much of the accumulating retirement benefit you get to keep if you leave the company. If your plan is different, you may want to consult Human Resources and have someone explain how it works.