The northern and western sections of Vietnam are dominated by the mountains of the Annamese Cordillera, continuations of the mountains of the Chinese provinces of Yunnan and Guangxi to the north. The mountains reach elevations of more than 8,000 ft (2,440 m), and contain a notable plateau known as the Central Highlands (alt. 600–1,600 ft/180–490 m), which, although sparsely populated, contains rubber, coffee, and tea plantations. East of the Annamese Cordillera in the north is an alluvial plain drained by the Red River and other streams that empty into the Gulf of Tonkin. South of the Red River delta are the Central Lowlands, a narrow, coastal strip where short, often torrential rivers, flowing from west to east, form fertile deltas. The alluvial plain of the Mekong River delta forms the southern portion of the country. The country has a tropical monsoon climate, modified by local conditions.
The population is concentrated in the two main river deltas. The Vietnamese account for more than 85% of the population. They speak an Annamese-Muong language (see Southeast Asian languages). The approximately 50 minority groups in the highlands include the Muong, Tai, Hmong, Dao, Sedong, Jarai, Bahnar, Rhade, Cham, and smaller groups. There is a significant population of Cambodians (Khmers) near the Cambodian border and at the mouth of the Mekong River. There are large numbers of Chinese in the urban centers, although many fled after South Vietnam was defeated by the North and after a border clash with China in 1979.
A mix of Buddhism, Confucianism, and traditional local beliefs and Roman Catholicism are the most widely practiced religions. Although the Communist government has discouraged religious practice, it is tolerated within the context of government-regulated Buddhist and Catholic groups, and since the 1990s traditional worship at Buddhist temples has been encouraged. Protestant evangelical churches (found mainly among ethnic minorities) and other unregulated groups are actively suppressed. Vietnamese is the official language, and English is increasingly favored as a second language. French, Chinese, Khmer, and languages of the various minority groups are also spoken.