Overview of editorial structure
There are tens of thousands of regular editors - everyone from expert scholars to casual readers. With the exception of blocked users, anyone who visits the site can edit it, and this fact has encouraged contribution of a tremendous amount of content. There are mechanisms that help community members watch for bad edits, a few hundred administrators with special powers to enforce good behavior, and a judicial style arbitration committee that considers the few situations remaining unresolved, and decides on withdrawal or restriction of editing privileges or other sanctions when needed, after all other consensus remedies have been tried.
As it's a wiki, anyone can contribute to Wikipedia, and everyone is encouraged to. Overall Wikipedia gets hundreds of times more well-meaning editors than bad ones, so problematic editors rarely obtain much of a foothold. In the normal course of events, the primary control over editorship is the effective utilization of the large number of well-intentioned editors to overcome issues raised by the much smaller number of problematic editors. It is inherent in the Wikipedia model's approach that poor information can be added, but that over time those editing articles reach strong consensus, and quality improves in a form of group learning, so that substandard edits will rapidly be removed. This assumption is still being tested and its limitations and reliability are not yet a settled matter – Wikipedia is a pioneer in communal knowledge building of this kind.
Balancing this, there are also a wide range of resources for editors seeking to improve their articles or within their areas of interest. These include several routes for general and specialist peer review, and thousands of editors in a wide variety of focus groups working on specific types of issue, reference desks and copyright resource checking to help source missing information, expert groups in various subjects for technical input, and subject related 'WikiProjects' which provide a comprehensive unified approach to editorial quality control and article rating in their respective subject areas.
The Wikipedia community is largely self-organizing, so that anyone may build a reputation as a competent editor and become involved in any role they may choose, subject to peer approval. Individuals often will choose to become involved in specialized tasks, such as reviewing articles at others' request, watching current edits for vandalism, or watching newly created articles for quality control purposes, or similar roles. Editors who find that editorial administrator responsibility would benefit their ability to help the community may ask their peers in the community for agreement to undertake such roles; a structure which enforces meritocracy and communal standards of editorship and conduct. At present around a 75–80% approval rating after a communal "no holds barred" inquiry, is considered the requirement for such a role, a standard which tends to ensure a high level of experience, trust and familiarity across a broad front of projects within Wikipedia.
(Such rights are stringently restricted, ensuring that editorial and administrative matters are separated powers and only rarely lead to editorial conflict of interest.)