Guerrilla warfare is a form of unconventional warfare in which small groups of irregular military use ambushes, sabotage, terrorism, raids, petty warfare or hit-and-run tactics. Guerrilla combatants use their familiarity with the local landscape and terrain to their advantage.

Guerilla tactics prolonged the conflict and posed significant challenges to traditional military strategies. It resulted in many casualties, as well as significant losses to South Vietnam and its allies. So much so, that many within the United States were conflicted on why the country had joined the war to begin with.

There's no telling exactly what the outcome would have looked like, however, the war wouldve more than likely been prolonged as their wouldn't have been as much of a massacre from the North on the South to culminate such a war. It could've still been a bloodbath that ended with either side becoming the victor, but "what ifs" don't apply in history.

Guerilla warfare matters for many reasons. It's a very strategic tactic that provides camoflauge while knowing their way around. It also makes for provided enough cover for stealthy attacks to catch the enemy by surprise, which often worked.