Interesting timing to me considering recent activity by Russia in Syria.
The United Nations Security Council (UNSC) - Council on Foreign Relations
"Introduction
The Security Council is the United Nations' principal crisis-management body, empowered to impose binding obligations on the UN's 193 member states to maintain peace. The council's five permanent and ten elected members meet regularly to assess threats to international security, addressing issues that include civil wars, natural disasters, arms control, and terrorism. Structurally, the body remains largely unchanged since its founding in 1946, stirring debate among many members about its efficacy and legitimacy as an arbiter on matters of international security. Syria's civil war poses particular challenges to the Security Council amid concerns about regional instability, proliferation, and a mounting humanitarian crisis. Similarly, Russia’s frictions with the United States and European Union following its actions in Ukraine in early 2014 have introduced new tensions into the council.
What is the Security Council’s structure?
The Security Council comprises five permanent members (P5)—China, France, the Russian Federation, the United Kingdom, and the United States—any one of whom can veto a resolution. The council’s ten elected members, who serve two-year nonconsecutive terms, are not afforded veto power. The P5's privileged status has its roots in the UN's founding in the aftermath of World War II. The United States and Russia (then the Soviet Union) were the outright victors of the war, and, along with the United Kingdom, they shaped the postwar political order. As their plans for what would become the United Nations took shape, U.S. President Franklin Delano Roosevelt insisted on Nationalist China's inclusion at the helm, envisioning international security presided over by "four global policemen." British Prime Minister Winston Churchill saw in France a European buffer against potential German or Soviet aggression and so sponsored its bid for restored great-power status.
The members of the P5 have chosen to exercise their ability to veto Council resolutions to varying degrees. Counting the years when the Soviet Union held the seat, Russia has been the most frequent user of its veto power in the Security Council, having exercised the right to block more than one hundred resolutions since the council’s founding. The United States is the second most frequent user of the veto. The United Kingdom, France, and China use their vetoes sparingly. China’s use of the veto has risen notably in recent years. In 2014, China joined Russia in vetoing a council resolution that would have referred actors in the Syrian Civil War, including the Bashar al-Assad regime, to the International Criminal Court.
The council's presidency rotates on a monthly basis, ensuring some agenda-setting influence for its ten nonpermanent members, who are elected by a two-thirds vote of the General Assembly. The main criterion for eligibility is contribution "to the maintenance of international peace and security," often defined by financial or troop contributions to peacekeeping operations or leadership on matters of regional security likely to appear before the council.
A secondary consideration, "equitable geographical distribution," gave rise to the regional groups used since 1965 in elections: the African Group has three seats; the Asia-Pacific Group, two; the Eastern European Group, one; GRULAC (Latin America and the Caribbean), two; and WEOG (Western Europe and Other Groups), two. Each has its own electoral norms. An Arab seat alternates between the African and Asian blocs by informal agreement. Turkey and Israel, which has never served on the council, caucus with WEOG.
Subsidiary organs that support the council's mission include ad hoc committees on sanctions, counterterrorism, and the nonproliferation of nuclear, biological, and chemical weapons, and international criminal tribunals for Rwanda and the former Yugoslavia. Within the UN Secretariat, the Department of Peacekeeping Operations and Department of Field Support manage field operations. The Peacebuilding Commission, established in 2005 as a repository of institutional memory and best practices in peacebuilding, serves an advisory role.
What are the Security Council’s tools for conflict management?
The Security Council aims to reach peaceful resolution of international disputes under Chapter VI of the UN Charter, which authorizes the council to call on parties to seek a solution via negotiation, arbitration, or other peaceful means. Failing that, Chapter VII empowers the Security Council to take more assertive action, such as imposing sanctions or authorizing the use of force "to maintain or restore international peace and security." Peacekeeping missions are the most visible face of the UN's conflict-management work; in mid-2015 the council was overseeing sixteen operations and nearly 105,000 uniformed personnel.
Constrained by U.S.-Soviet rivalry, the Security Council acted infrequently in the four-and-a-half decades between its founding and the close of the Cold War in 1989. During that time it authorized seventeen peacekeeping operations. Since 2014, heightened tensions between the United States and Russia have manifested anew in the council, leading to concerns that it may be less able to act when faced with crises. For example, in July 2015, Russia vetoed a resolution that would have created an international tribune to prosecute the pro-Russia separatists in eastern Ukraine who are thought to have shot down Malaysian Airlines flight MH17 using a Russian-made missile.
The Security Council has authorized fifty-one operations in the years since the Cold War, many responding to failing states, civil wars, or complex humanitarian emergencies, and deploying to conflict zones in the absence of cease-fires or parties' consent. Under more muscular mandates, they have combined military operations—including less restrictive rules of engagement that allow for civilian and refugee protection—with civilian tasks, including policing, electoral assistance, and legal administration. Developing nations provide the lion's share of personnel".
Rest of article in the link