Permanent members of the United Nations Security Council
The permanent members of the United Nations Security Council (also known as the Permanent Five, Big Five, or P5) are the five states which the UN Charter of 1945 grants a permanent seat on the UN Security Council: China (formerly the Republic of China), France, Russia (formerly the Soviet Union), the United Kingdom, and the United States. These countries were all allies in World War II, which they won. They are also all nuclear weapons states. A total of 15 UN member states serve on the UNSC, the remainder of which are elected. Any one of the five permanent members have the power of veto, which enables them to prevent the adoption of any "substantive" draft Council resolution, regardless of its level of international support.
Supermajority
The United Nations Security Council requires a supermajority of the fixed membership on substantive matters (procedural matters require a simple majority of those present and voting). According to Article 27 of the United Nations Charter, at least nine of the Security Council's 15 members (i.e., a three-fifths supermajority) must vote in favor of a draft resolution in order to achieve passage. Specifying the fixed membership has the effect of making abstentions count as votes against—absences are not normal but would be treated the same way.