Consensus is the main way decisions are made on Wikipedia, both in terms of article content and how Wikipedia itself is run. Wikipedia's concept of consensus doesn't necessarily mean that everyone agrees, but it involves an effort to incorporate all editors' legitimate concerns, while respecting Wikipedia's policies and guidelines.
When disagreements occur, we resolve them through discussion—usually on the relevant Talk page. Since Wikipedia articles should be written from a neutral point of view—fairly describing significant viewpoints on a subject without endorsing any of them—it is almost always possible to reach consensus about article content, even if editors themselves have fundamentally different points of view on the subject.
The ideal Wikipedia article on a controversial topic is one where partisans on both sides would read it and say, "my viewpoint is described accurately".