They are continually edited and (usually) improved over time.
In general this results in an upward trend of quality and a growing consensus over a fair and balanced representation of information.
However, this process can take months or years, as each user contributes in turn.
Some articles contain statements and claims that have not yet been fully cited. Some information now in the article may be considered by later contributors to be insufficiently founded and may be removed or expanded.
Similarly, it is one of the few sites on the web even attempting neutral, objective, encyclopedic coverage of popular culture, including television series or science fiction.
It is also developing across-the-board global coverage of subject areas where for one reason or another existing sources are highly fragmented, including sports such as football/soccer and golf.
While the overall trend is generally upward, it is not uniformly upward.
It is important to use Wikipedia carefully if it is intended to be used as a research source.
This may be almost impossible to find anywhere other than Wikipedia, unless you read Armenian, which you probably don’t, or are prepared to spend an hour in the library, which you probably don’t want to. Increasingly Wikipedia information will be referenced with academic references.
In this case, you should rely on–and cite–Wikipedia. Hopefully when you see a fact in Wikipedia you will be able to quickly verify it with an online, academic source, which you can cite instead of Wikipedia.