How to record define benefit pension plan on financial statements?

What are the differences between defined-benefit pension plans and defined-contribution pension plans? How is each recorded in the financial statements? What are some of the challenges that the company may face in maintaining these types of pension plans? Why have companies abandoned certain types of pension plans? What are some examples of organizations abandoning certain types of pension plans? When does the Pension Benefit Guaranty Corporation (PBGC) become involved with private companies' pensions? What role does the PBGC play in managing and implementing these pension plans? What is the main difference in estimating the liability associated with pensions versus other post-employment benefits? What makes estimating post-retirement health care benefits so difficult