The UN Peacebuilding Architecture consists of the Peacebuilding Commission (PBC), the Peacebuilding Support Office (PBSO) and the Peacebuilding Fund (PBF). Although most of the UN's bodies play an important role in peacebuilding, this cluster of three new bodies was added in 2005-6 to the system to strengthen UN's efforts to help countries build sustainable peace and prevent relapse into violent conflict. You can read more about the tasks and mandates of each body here.
A first review of the Peacebuilding Architecture was conducted in 2010 and concluded that five years after its inception, the PBC was still to realize its full potential, although it did enjoy support and commitment from Member States. The General Assembly and Security Council called for another review to be conducted in 2015 to examine the progress made and "propose ways to strengthen the performance and impact of the Peacebuilding Architecture, with a view to realizing its full potential."
This review, titled ‘The Challenge of Sustaining Peace - the Report of the Advisory Group of Experts on the United Nations Peacebuilding Architecture', or the AGE report. The publication of the AGE report coincided with two other major reports on UN's peacebuilding and peacekeeping work; the Global Study on the Implementation of Security Council Resolution 1325 on women, peace and security and the High-level Independent Panel on UN Peace Operations as well as the Secretary General's recommendations for implementation. You can read about the linkages between the three reports here.
Particularly the review of the Peacebuilding Architecture, which coined the term sustaining peace, gave impetus to the resolutions adopted by the Security Council (S/RES/2282(2016)) and the General Assembly (A/RES/70/305). These identical resolutions on the Review of United Nations Peacebuilding Architecture are also known as the sustaining peace resolutions.