What is a pension plan as used in a firm and related to employee compensation?

What is a pension plan as used in a firm and related to employee compensation? What is the difference between a defined contribution plan and a defined benefit plan? What is accumulated benefit obligation and how is such associated with a projected benefit obligation? What is the funded status and where is it reported? How does a firm report post retirement benefits in accounting statements? What is an actuary and what is the actuary’s duty in this process? What are the legal considerations of such plans and what government agencies exercise control? Provide a discussion of all potential scenarios and the relevant accounting requirements