Short answers, pulled from the story.
The five nations that hold permanent seats on the United Nations Security Council are France, China, the Soviet Union (now Russia), the United Kingdom, and the United States. These states emerged as victorious Allies from World War II and secured their status when the UN Charter came into force in 1945.
The People's Republic of China officially became the legal representative of China at the United Nations through General Assembly Resolution 2758 passed in 1971. This decision expelled the Republic of China from the organization entirely after it lost control of mainland China during the Chinese Civil War.
Any one of the five permanent members can block a non-procedural resolution regardless of global support levels using a mechanism known as the veto. A negative vote from any P5 member prevents adoption of such resolutions while abstention or absence does not stop passage of a draft.
Data from January 2020 shows that Russia held nearly 6,000 warheads while the United States led with roughly 5,400 units. China possessed around 600 warheads and France maintained approximately 290 whereas the UK had about 225 active nuclear weapons.
Brazil, Germany, India, and Japan form a group known as G4 seeking permanent seats on the council by mutually supporting one another's bids. Despite repeated attempts at reform since 1992 no changes have been made to Article 23 of the UN Charter to include these nations.