During the Vietnam War, the United States were fighting two armies: North Vietnam and the Viet Cong, a guerrilla style army based in South Vietnam and Cambodia. Beginning in the First Indochina War, this helped maintain communication with North and South Vietnam.
There were constantly forces trying to disrupt the trail, including Pathet Lao forces in 1958, which caused the Ho Chi Minh Trail to change, going west of the Annamese mountains. In 1959, the trail was only used for infiltrating manpower, due to the fact that North Vietnam could bring resources to the Viet Cong much easier by sea.
Later, as the US starting knowing the trail better, they changed the trail into a series of fie base areas, where goods and resources would be stored to be transferred to the next base area. That made it much harder to intercept goods. Eventually, the system developed into an intricate maze of a 5.5 meter wide.
Overall, it was essential in the Viet Cong/ North Vietnam victory, and it was an amazing work of engineering.