Anywhere they were at was VC territory. But primarily in the Mekong Delta; the NVA had a long enough distance to march as it was (down the Ho Chi Minh Trail from North Vietnam), so the NVA operated in III Corps (Saigon AO) only during the Tet Offensive and related actions, then stayed in the Highlands (II Corps) and I Corps regions; leaving the Delta (IV Corps) to the VC.
In the 1970's, (generally speaking) III & IV Corps (MR=Military Regions 3 & 4) were VC country and II and I Corps were NVA territory. With I Corps being the worst (place to be). In I Corps, the NVA hunted for you (the GI).
Cong is short for Viet Cong. The Viet Cong were the communist guerrilla forces backed by North Vietnam when they fought against South Vietnam during the Vietnam War.
Viet Congs: North communist Vietnamese supporters of the communist Front in North Vietnam during the Vietnam War (known in Vietnam as the American War). The Viet Congs fought against both the government/military of South Vietnam and the armed forces of the United States between 1959 and 1975. They were initially a loose grouping of guerrilla fighters. Quick Note: South Vietnam/South Vietnamese didn't want the communist takeover from communist North Vietnam, they wanted to be a democratic country. U.S. entered the war to stop the spread of communism and support the democratic South Vietnam.
To get new or more land for their country. In other words to expand their territory.
Viet Minh
The Viet Minh were the Viet Cong of the 1946-1954 French Indochina war.
Generally a non-uniformed, non-formally trained, mostly non-paid soldier. Although regular Government soldiers, marines, airmen, and sailors CAN be detailed the duties of guerrillas...generally guerrillas are as described in the first sentence. Although, it should be noted, that the VC were one of history's most successful guerrilla fighters.
•Viet Mihn • Viet Cong
The population of Viet Tri is 260,288.
Viet Cong was created in 1954.
Viet Cong ended in 1976.
Viet Museum was created in 2007.
Viet Linh was born in 1952.