Short answers, pulled from the story.
Vietnam sits at the eastern edge of Mainland Southeast Asia. It is bordered by China to the north and by Laos and Cambodia to the west. It lies along the Gulf of Thailand to the southwest and the South China Sea to the east.
Vietnam has a population of over 102 million, making it the world's 16th-most populous country. It covers an area of about 331,000 square kilometres. Its capital is Hanoi and its largest city is Ho Chi Minh City.
Northern Vietnam was mostly under Chinese rule for about a thousand years, beginning when the Han dynasty incorporated the region into its empire in 111 BC. Full independence came in 939, when the Vietnamese lord Ngô Quyền defeated the Chinese Southern Han state at the Bạch Đằng River.
The Vietnam War ended with the fall of Saigon on the 30th of April 1975. On the 2nd of July 1976, North and South Vietnam merged to form the Socialist Republic of Vietnam under the Communist Party of Vietnam.
Đổi Mới, meaning Renovation, was a series of market reforms launched by the Communist Party of Vietnam at its Sixth National Congress in December 1986. It managed the transition from a planned economy to a socialist-oriented market economy, encouraging private ownership and foreign investment while keeping state control over strategic industries.
The name Việt Nam means Viet of the South per Vietnamese word order. The form is first recorded in the 16th-century oracular poem Sấm Trạng Trình. Emperor Gia Long sought the title Nam Việt in 1802, but the Jiaqing Emperor of the Qing dynasty chose Việt Nam instead.
Hang Sơn Đoòng is among the largest caves in the world, first surveyed in 2009 by an expedition from the British Cave Research Association. It runs over 8.8 kilometres long, with caverns large enough to hold a 40-story skyscraper and a sinkhole more than 183 metres deep, beneath which grows a tropical rainforest.