Fundamentally, a controversy has two sides. Often, each side has their own version of "the truth" which can paint a different picture of a situation, based on whose "truth" gets used in a Wikipedia article. Combine that with the fact that "truth" has a logical, factual, and ethical meaning, and the concept of publishing the truth becomes difficult to execute.
This can lead to some odd situations. As an example, if all videos and personal accounts surrounding an event are erased for some reason (war, natural disaster, etc.) and the even can no longer be verified, did it not exist? It's similar to the thought experiment, "If a tree falls in a forest and no one is around to hear it, does it make a sound?"
Let's all discuss the concept of reality and perception! Or, you know, let's not.
Wikipedia deals with this by dodging the question of truth almost entirely. Wikipedia lets others figure out what the truth is and published their thoughts instead of creating their own thoughts on what the truth is. Letting others decide what the truth is, is essentially what "verifiability" refers to on Wikipedia.
If something is verifiable, it can be covered. If there is a controversy where reliable sources are arguing about what the truth is, cover the controversy.
As someone who wants to add information to Wikipedia, remembering this concept is important. Essentially, Wikipedia doesn't exactly care what you believe the truth to be. It cares about what you can verify. If you go to Wikipedia attempting to add truth instead of verifiable information, there's a good chance you'll be met with resistance.
This is especially important for "Biographies of living persons" - a topic we'll discuss in the near future.