Khmer People is about 14.86 million (2012) which about 90-95 percent of all populations. They speak Khmer Languages which known as is part of the larger Mon–Khmer language family found throughout Southeast Asia.
The majority of the Khmer are followers of the Khmer style of Buddhism, a highly syncretic version which blends elements of Theravada Buddhism, Hinduism, animism and ancestor-spirit worship. Significant populations of Khmers reside in adjacent areas of Thailand (Khmer Leu) and the Mekong Delta region of neighboring Vietnam (Khmer Krom).
About 10 percent of the population lives in Phnom Penh, the capital, making Cambodia largely a country of rural dwellers, farmers and artisans. The majority of the Cambodian are living permanently along the bodies of water in the Tonle Sap Basin-Mekong and Tonlesap Lake region. The Khmer Loeu live in widely scattered villages that are abandoned when the cultivated land in the vicinity is exhausted. The permanently settled Khmer and Cham villages usually located on or near the banks of a river or other bodies of water. Cham villages usually are made up almost entirely of Cham, but Khmer villages, especially in central and in southeastern of Cambodia.
From the History:
Khmers (Cambodia Today); begin its history by founders of the kingdom of Kambuja, the Brahman
Sage_Kambu_Swayambhuva and the naga princess Mera’s names, is said to have given rise to the name Khmer.
Migrations into the mainland regions of Southeast Asia from the north continued well into historic times. Most scholars believe Khmers came at least 3,000 years ago, much earlier than Tai people who now inhabit many parts of what was originally Austroasiatic territory. The reason they migrated into Southeast Asia is generally debated, but scholars believe that Mon–Khmer were pushed down by invading Sino-Tibetans from the north as evident by Austroasiatic vocabulary in Chinese or because of agricultural purposes as evident by their migration routes along major rivers. The Khmer are relatives to the Mon who settled further to the west.
After establishment in Southeast Asia, the history of the Khmers began the history of Cambodia. Like the other early peoples of Southeast Asia such as the Pyu, Mon, Cham, Malay and Javanese, the Khmer were influenced by Indian and Sri Lankan traders and scholars, adopting their religions, sciences, and customs and borrowing from their languages.
The Khmer also acquired the concept of the Shaivite Deva Raja (God-King) and the great temple as a symbolic holy mountain. Although Cambodian kingdoms waxed and waned and were eventually eclipsed, the Cambodian penchant for building temples of stone throughout their kingdoms left monuments still extant today.