The current Wikipedia entry for Net Neutrality has a pretty good intro, but you never know how long these things will last:
Columbia University law professor Tim Wu popularized the phrase network neutrality as a term designating a network that does not favor one application (for example the World Wide Web) over another (such as online gaming or Voice over IP). Wu claims that the Internet is not neutral “as among all applications” as it favors file transfer over real-time communication.
The concept of network neutrality has since taken the form of various regulations proposed to govern Internet communications, including commercial interconnection agreements between Internet Service Providers (ISPs), carriers, on-line service providers, and broadband users, usually on the basis of principles of public service obligations associated with special access to public rights of way. In this sense, network neutrality means a state in which Internet providers provide interconnection services on a uniform basis, or “without discrimination”, although there is considerable disagreement about how this principle applies to applications with different needs.
Network neutrality is sometimes used as a technical term, although it has no history in the design documents (RFCs) describing the Internet protocols. In this usage, it is claimed to represent a property of protocol layering in which higher-layer protocols may not communicate service requirements to lower-layer protocols, a highly idiosyncratic interpretation of protocol engineering. (In conventional network engineering practice, each protocol in a layered system exposes Service Access Points to higher layers that can be used to request a level of service appropriate to the needs of higher-layer protocols.
Network neutrality also designates a contemporary controversy local to the United States regarding the role that government should take relative to Internet access providers providing multiple levels of service for different fees. This controversy, which emerged following regulatory developments in the United States, is extremely complex, as it mixes technical, economic, ideological and legal arguments. In essence, network neutrality regulations proposed by Senators Snowe and Dorgan and Representative Markey bar ISPs from offering Quality of Service enhancements for a fee.
High-traffic articles in Wikipedia tend to degrade over time and require reformulation as entropy increases.
UPDATE: That didn’t take long. A Google sympathizer going by the name “Wolfkeeper” tried to erase the summary and replace it with a pithy personal opinion. See the history page.